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	$143.27	6.597%	$152.7215	$152.72	$152.70	$152.70
Purchase #2	$132.75	6.634%	$141.5566	$141.56	$141.55	$141.60
Purchase #3	$80.39	11.639%	$89.7466	$89.75	$89.75	$89.70
Purchase #4	$92.94	8.754%	$101.076	$101.08	$101.10	$101.10
Purchase #5	$83.74	11.672%	$93.5141	$93.51	$93.50	$93.50
Purchase #6	$5.79	8.361%	$6.2741	$6.27	$6.25	$6.30
Purchase #7	$169.77	3.343%	$175.4454	$175.45	$175.45	$175.40
7 purchase totals =	$708.65		$760.3343	$760.34	$760.30	$760.30