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	$54.43	9.722%	$59.7217	$59.72	$59.70	$59.70
Purchase #2	$101.67	3.444%	$105.1715	$105.17	$105.15	$105.20
Purchase #3	$139.79	9.869%	$153.5859	$153.59	$153.60	$153.60
Purchase #4	$69.56	4.519%	$72.7034	$72.70	$72.70	$72.70
Purchase #5	$77.55	10.569%	$85.7463	$85.75	$85.75	$85.70
Purchase #6	$55.72	10.501%	$61.5712	$61.57	$61.55	$61.60
Purchase #7	$58.86	9.199%	$64.2745	$64.27	$64.25	$64.30
7 purchase totals =	$557.58		$602.7745	$602.77	$602.70	$602.80