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	$222.72	13.823%	$253.5066	$253.51	$253.50	$253.50
Purchase #2	$13.91	10.318%	$15.3452	$15.35	$15.35	$15.30
Purchase #3	$83.68	13.367%	$94.8655	$94.87	$94.85	$94.90
Purchase #4	$53.91	9.528%	$59.0465	$59.05	$59.05	$59.00
Purchase #5	$53.90	13.682%	$61.2746	$61.27	$61.25	$61.30
Purchase #6	$205.67	11.649%	$229.6285	$229.63	$229.65	$229.60
Purchase #7	$44.99	11.417%	$50.1265	$50.13	$50.15	$50.10
7 purchase totals =	$678.78		$763.7934	$763.81	$763.80	$763.70