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	$177.92	4.223%	$185.4336	$185.43	$185.45	$185.40
Purchase #2	$157.60	11.647%	$175.9557	$175.96	$175.95	$176.00
Purchase #3	$207.52	4.402%	$216.655	$216.66	$216.65	$216.70
Purchase #4	$111.45	12.245%	$125.0971	$125.10	$125.10	$125.10
Purchase #5	$119.73	10.112%	$131.8371	$131.84	$131.85	$131.80
Purchase #6	$37.94	7.775%	$40.8898	$40.89	$40.90	$40.90
Purchase #7	$29.62	5.165%	$31.1499	$31.15	$31.15	$31.10
7 purchase totals =	$841.78		$907.0182	$907.03	$907.05	$907.00