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	$53.80	13.560%	$61.0953	$61.10	$61.10	$61.10
Purchase #2	$33.89	8.743%	$36.853	$36.85	$36.85	$36.90
Purchase #3	$172.98	5.782%	$182.9817	$182.98	$183.00	$183.00
Purchase #4	$65.40	12.741%	$73.7326	$73.73	$73.75	$73.70
Purchase #5	$148.92	13.584%	$169.1493	$169.15	$169.15	$169.10
Purchase #6	$158.87	10.444%	$175.4624	$175.46	$175.45	$175.50
Purchase #7	$155.77	10.485%	$172.1025	$172.10	$172.10	$172.10
7 purchase totals =	$789.63		$871.3768	$871.37	$871.40	$871.40