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	$185.90	13.205%	$210.4481	$210.45	$210.45	$210.40
Purchase #2	$105.83	11.874%	$118.3963	$118.40	$118.40	$118.40
Purchase #3	$180.94	10.171%	$199.3434	$199.34	$199.35	$199.30
Purchase #4	$83.45	6.208%	$88.6306	$88.63	$88.65	$88.60
Purchase #5	$163.79	5.335%	$172.5282	$172.53	$172.55	$172.50
Purchase #6	$228.54	8.656%	$248.3224	$248.32	$248.30	$248.30
Purchase #7	$79.98	10.607%	$88.4635	$88.46	$88.45	$88.50
7 purchase totals =	$1,028.43		$1,126.1325	$1,126.13	$1,126.15	$1,126.00