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	$246.76	11.325%	$274.7056	$274.71	$274.70	$274.70
Purchase #2	$169.34	12.474%	$190.4635	$190.46	$190.45	$190.50
Purchase #3	$111.93	3.275%	$115.5957	$115.60	$115.60	$115.60
Purchase #4	$62.63	11.846%	$70.0491	$70.05	$70.05	$70.00
Purchase #5	$35.98	3.413%	$37.208	$37.21	$37.20	$37.20
Purchase #6	$230.52	11.170%	$256.2691	$256.27	$256.25	$256.30
Purchase #7	$113.44	12.651%	$127.7913	$127.79	$127.80	$127.80
7 purchase totals =	$970.60		$1,072.0823	$1,072.09	$1,072.05	$1,072.10