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	$60.89	3.653%	$63.1143	$63.11	$63.10	$63.10
Purchase #2	$140.75	3.290%	$145.3807	$145.38	$145.40	$145.40
Purchase #3	$209.84	11.680%	$234.3493	$234.35	$234.35	$234.30
Purchase #4	$65.54	10.468%	$72.4007	$72.40	$72.40	$72.40
Purchase #5	$229.93	12.455%	$258.5678	$258.57	$258.55	$258.60
Purchase #6	$59.29	4.131%	$61.7393	$61.74	$61.75	$61.70
Purchase #7	$45.60	11.649%	$50.9119	$50.91	$50.90	$50.90
7 purchase totals =	$811.84		$886.4640	$886.46	$886.45	$886.40