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	$97.96	12.635%	$110.3372	$110.34	$110.35	$110.30
Purchase #2	$52.87	12.718%	$59.594	$59.59	$59.60	$59.60
Purchase #3	$151.43	13.293%	$171.5596	$171.56	$171.55	$171.60
Purchase #4	$162.60	6.658%	$173.4259	$173.43	$173.45	$173.40
Purchase #5	$217.64	8.418%	$235.9609	$235.96	$235.95	$236.00
Purchase #6	$6.51	6.472%	$6.9313	$6.93	$6.95	$6.90
Purchase #7	$221.63	10.439%	$244.766	$244.77	$244.75	$244.80
7 purchase totals =	$910.64		$1,002.5749	$1,002.58	$1,002.60	$1,002.60