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	$229.57	10.236%	$253.0688	$253.07	$253.05	$253.10
Purchase #2	$134.83	10.192%	$148.5719	$148.57	$148.55	$148.60
Purchase #3	$234.29	11.623%	$261.5215	$261.52	$261.50	$261.50
Purchase #4	$249.55	5.674%	$263.7095	$263.71	$263.70	$263.70
Purchase #5	$158.28	6.625%	$168.7661	$168.77	$168.75	$168.80
Purchase #6	$55.51	7.243%	$59.5306	$59.53	$59.55	$59.50
Purchase #7	$148.46	7.674%	$159.8528	$159.85	$159.85	$159.90
7 purchase totals =	$1,210.49		$1,315.0212	$1,315.02	$1,314.95	$1,315.10