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	$204.97	3.664%	$212.4801	$212.48	$212.50	$212.50
Purchase #2	$231.76	9.342%	$253.411	$253.41	$253.40	$253.40
Purchase #3	$234.76	13.102%	$265.5183	$265.52	$265.50	$265.50
Purchase #4	$157.56	9.412%	$172.3895	$172.39	$172.40	$172.40
Purchase #5	$62.57	4.639%	$65.4726	$65.47	$65.45	$65.50
Purchase #6	$135.90	13.707%	$154.5278	$154.53	$154.55	$154.50
Purchase #7	$134.56	10.273%	$148.3833	$148.38	$148.40	$148.40
7 purchase totals =	$1,162.08		$1,272.1826	$1,272.18	$1,272.20	$1,272.20