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	$86.45	8.657%	$93.934	$93.93	$93.95	$93.90
Purchase #2	$153.89	13.174%	$174.1635	$174.16	$174.15	$174.20
Purchase #3	$215.48	3.285%	$222.5585	$222.56	$222.55	$222.60
Purchase #4	$148.39	3.209%	$153.1518	$153.15	$153.15	$153.20
Purchase #5	$69.63	10.330%	$76.8228	$76.82	$76.80	$76.80
Purchase #6	$80.74	11.381%	$89.929	$89.93	$89.95	$89.90
Purchase #7	$149.48	11.476%	$166.6343	$166.63	$166.65	$166.60
7 purchase totals =	$904.06		$977.1939	$977.18	$977.20	$977.20