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	$201.87	3.188%	$208.3056	$208.31	$208.30	$208.30
Purchase #2	$217.51	12.592%	$244.8989	$244.90	$244.90	$244.90
Purchase #3	$106.77	4.652%	$111.7369	$111.74	$111.75	$111.70
Purchase #4	$239.91	12.375%	$269.5989	$269.60	$269.60	$269.60
Purchase #5	$191.61	9.361%	$209.5466	$209.55	$209.55	$209.50
Purchase #6	$83.33	7.869%	$89.8872	$89.89	$89.90	$89.90
Purchase #7	$118.58	9.613%	$129.9791	$129.98	$130.00	$130.00
7 purchase totals =	$1,159.58		$1,263.9532	$1,263.97	$1,264.00	$1,263.90