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	$168.33	9.822%	$184.8634	$184.86	$184.85	$184.90
Purchase #2	$135.72	4.374%	$141.6564	$141.66	$141.65	$141.70
Purchase #3	$145.33	13.114%	$164.3886	$164.39	$164.40	$164.40
Purchase #4	$53.74	8.709%	$58.4202	$58.42	$58.40	$58.40
Purchase #5	$78.29	12.807%	$88.3166	$88.32	$88.30	$88.30
Purchase #6	$138.88	12.568%	$156.3344	$156.33	$156.35	$156.30
Purchase #7	$89.50	13.667%	$101.732	$101.73	$101.75	$101.70
7 purchase totals =	$809.79		$895.7116	$895.71	$895.70	$895.70