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	$24.82	3.525%	$25.6949	$25.69	$25.70	$25.70
Purchase #2	$161.89	4.157%	$168.6198	$168.62	$168.60	$168.60
Purchase #3	$155.27	9.338%	$169.7691	$169.77	$169.75	$169.80
Purchase #4	$68.55	3.355%	$70.8499	$70.85	$70.85	$70.80
Purchase #5	$61.52	4.449%	$64.257	$64.26	$64.25	$64.30
Purchase #6	$74.82	4.817%	$78.4241	$78.42	$78.40	$78.40
Purchase #7	$12.58	12.300%	$14.1273	$14.13	$14.15	$14.10
7 purchase totals =	$559.45		$591.7421	$591.74	$591.70	$591.70