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	$248.77	10.268%	$274.3137	$274.31	$274.30	$274.30
Purchase #2	$243.57	10.312%	$268.6869	$268.69	$268.70	$268.70
Purchase #3	$190.82	7.833%	$205.7669	$205.77	$205.75	$205.80
Purchase #4	$247.85	11.563%	$276.5089	$276.51	$276.50	$276.50
Purchase #5	$124.69	5.852%	$131.9869	$131.99	$132.00	$132.00
Purchase #6	$111.56	4.525%	$116.6081	$116.61	$116.60	$116.60
Purchase #7	$180.83	8.546%	$196.2837	$196.28	$196.30	$196.30
7 purchase totals =	$1,348.09		$1,470.1551	$1,470.16	$1,470.15	$1,470.20