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	$97.86	4.726%	$102.4849	$102.48	$102.50	$102.50
Purchase #2	$88.69	8.131%	$95.9014	$95.90	$95.90	$95.90
Purchase #3	$28.39	11.629%	$31.6915	$31.69	$31.70	$31.70
Purchase #4	$81.32	11.560%	$90.7206	$90.72	$90.70	$90.70
Purchase #5	$14.41	6.863%	$15.399	$15.40	$15.40	$15.40
Purchase #6	$229.31	3.115%	$236.453	$236.45	$236.45	$236.50
Purchase #7	$33.96	10.136%	$37.4022	$37.40	$37.40	$37.40
7 purchase totals =	$573.94		$610.0526	$610.04	$610.05	$610.10