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	$114.66	13.597%	$130.2503	$130.25	$130.25	$130.30
Purchase #2	$155.58	3.428%	$160.9133	$160.91	$160.90	$160.90
Purchase #3	$65.91	7.374%	$70.7702	$70.77	$70.75	$70.80
Purchase #4	$148.34	11.703%	$165.7002	$165.70	$165.70	$165.70
Purchase #5	$106.33	7.741%	$114.561	$114.56	$114.55	$114.60
Purchase #6	$176.53	13.219%	$199.8655	$199.87	$199.85	$199.90
Purchase #7	$188.28	4.227%	$196.2386	$196.24	$196.25	$196.20
7 purchase totals =	$955.63		$1,038.2991	$1,038.30	$1,038.25	$1,038.40