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	$104.98	6.648%	$111.9591	$111.96	$111.95	$112.00
Purchase #2	$146.40	13.119%	$165.6062	$165.61	$165.60	$165.60
Purchase #3	$246.80	9.869%	$271.1567	$271.16	$271.15	$271.20
Purchase #4	$49.77	10.843%	$55.1666	$55.17	$55.15	$55.20
Purchase #5	$70.55	4.268%	$73.5611	$73.56	$73.55	$73.60
Purchase #6	$88.38	7.362%	$94.8865	$94.89	$94.90	$94.90
Purchase #7	$237.31	4.493%	$247.9723	$247.97	$247.95	$248.00
7 purchase totals =	$944.19		$1,020.3085	$1,020.32	$1,020.25	$1,020.50