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	$234.52	12.360%	$263.5067	$263.51	$263.50	$263.50
Purchase #2	$208.77	7.201%	$223.8035	$223.80	$223.80	$223.80
Purchase #3	$191.69	11.294%	$213.3395	$213.34	$213.35	$213.30
Purchase #4	$124.93	9.669%	$137.0095	$137.01	$137.00	$137.00
Purchase #5	$151.85	8.734%	$165.1126	$165.11	$165.10	$165.10
Purchase #6	$66.90	7.483%	$71.9061	$71.91	$71.90	$71.90
Purchase #7	$74.30	5.190%	$78.1562	$78.16	$78.15	$78.20
7 purchase totals =	$1,052.96		$1,152.8341	$1,152.84	$1,152.80	$1,152.80