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	$154.61	5.203%	$162.6544	$162.65	$162.65	$162.70
Purchase #2	$52.77	4.654%	$55.2259	$55.23	$55.25	$55.20
Purchase #3	$61.68	13.753%	$70.1629	$70.16	$70.15	$70.20
Purchase #4	$33.31	12.340%	$37.4205	$37.42	$37.40	$37.40
Purchase #5	$199.91	8.244%	$216.3906	$216.39	$216.40	$216.40
Purchase #6	$91.43	7.235%	$98.045	$98.05	$98.05	$98.00
Purchase #7	$172.81	12.785%	$194.9038	$194.90	$194.90	$194.90
7 purchase totals =	$766.52		$834.8031	$834.80	$834.80	$834.80