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	$55.87	7.126%	$59.8513	$59.85	$59.85	$59.90
Purchase #2	$211.27	11.517%	$235.602	$235.60	$235.60	$235.60
Purchase #3	$46.25	8.819%	$50.3288	$50.33	$50.35	$50.30
Purchase #4	$222.31	9.869%	$244.2498	$244.25	$244.25	$244.20
Purchase #5	$143.59	12.244%	$161.1712	$161.17	$161.15	$161.20
Purchase #6	$87.62	5.655%	$92.5749	$92.57	$92.55	$92.60
Purchase #7	$57.76	3.112%	$59.5575	$59.56	$59.55	$59.60
7 purchase totals =	$824.67		$903.3355	$903.33	$903.30	$903.40