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	$10.98	6.812%	$11.728	$11.73	$11.75	$11.70
Purchase #2	$101.36	8.380%	$109.854	$109.85	$109.85	$109.90
Purchase #3	$188.63	10.595%	$208.6153	$208.62	$208.60	$208.60
Purchase #4	$121.47	7.501%	$130.5815	$130.58	$130.60	$130.60
Purchase #5	$37.91	9.741%	$41.6028	$41.60	$41.60	$41.60
Purchase #6	$157.93	9.507%	$172.9444	$172.94	$172.95	$172.90
Purchase #7	$227.39	12.758%	$256.4004	$256.40	$256.40	$256.40
7 purchase totals =	$845.67		$931.7264	$931.72	$931.75	$931.70