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	$157.97	9.294%	$172.6517	$172.65	$172.65	$172.70
Purchase #2	$178.64	5.700%	$188.8225	$188.82	$188.80	$188.80
Purchase #3	$175.73	8.601%	$190.8445	$190.84	$190.85	$190.80
Purchase #4	$148.47	4.691%	$155.4347	$155.43	$155.45	$155.40
Purchase #5	$227.34	7.603%	$244.6247	$244.62	$244.60	$244.60
Purchase #6	$146.65	8.749%	$159.4804	$159.48	$159.50	$159.50
Purchase #7	$162.66	6.637%	$173.4557	$173.46	$173.45	$173.50
7 purchase totals =	$1,197.46		$1,285.3142	$1,285.30	$1,285.30	$1,285.30