Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.33	3.292%	$176.9702	$176.97	$176.95	$177.00
Purchase #2	$142.79	10.732%	$158.1142	$158.11	$158.10	$158.10
Purchase #3	$103.85	9.317%	$113.5257	$113.53	$113.55	$113.50
Purchase #4	$197.59	4.774%	$207.0229	$207.02	$207.00	$207.00
Purchase #5	$133.35	8.656%	$144.8928	$144.89	$144.90	$144.90
Purchase #6	$148.43	11.141%	$164.9666	$164.97	$164.95	$165.00
Purchase #7	$71.82	8.803%	$78.1423	$78.14	$78.15	$78.10
7 purchase totals =	$969.16		$1,043.6347	$1,043.63	$1,043.60	$1,043.60