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	$133.52	12.122%	$149.7053	$149.71	$149.70	$149.70
Purchase #2	$139.80	4.840%	$146.5663	$146.57	$146.55	$146.60
Purchase #3	$223.87	9.221%	$244.5131	$244.51	$244.50	$244.50
Purchase #4	$200.83	12.153%	$225.2369	$225.24	$225.25	$225.20
Purchase #5	$140.25	7.814%	$151.2091	$151.21	$151.20	$151.20
Purchase #6	$229.92	6.499%	$244.8625	$244.86	$244.85	$244.90
Purchase #7	$219.32	10.717%	$242.8245	$242.82	$242.80	$242.80
7 purchase totals =	$1,287.51		$1,404.9177	$1,404.92	$1,404.85	$1,404.90