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	$127.65	12.304%	$143.3561	$143.36	$143.35	$143.40
Purchase #2	$128.59	9.693%	$141.0542	$141.05	$141.05	$141.10
Purchase #3	$147.70	12.191%	$165.7061	$165.71	$165.70	$165.70
Purchase #4	$93.37	10.715%	$103.3746	$103.37	$103.35	$103.40
Purchase #5	$82.32	5.634%	$86.9579	$86.96	$86.95	$87.00
Purchase #6	$88.74	13.411%	$100.6409	$100.64	$100.65	$100.60
Purchase #7	$189.84	10.789%	$210.3218	$210.32	$210.30	$210.30
7 purchase totals =	$858.21		$951.4116	$951.41	$951.35	$951.50