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	$63.25	13.767%	$71.9576	$71.96	$71.95	$72.00
Purchase #2	$103.42	9.388%	$113.1291	$113.13	$113.15	$113.10
Purchase #3	$138.86	13.532%	$157.6505	$157.65	$157.65	$157.70
Purchase #4	$48.47	8.344%	$52.5143	$52.51	$52.50	$52.50
Purchase #5	$164.51	10.794%	$182.2672	$182.27	$182.25	$182.30
Purchase #6	$77.73	13.655%	$88.344	$88.34	$88.35	$88.30
Purchase #7	$88.36	13.530%	$100.3151	$100.32	$100.30	$100.30
7 purchase totals =	$684.60		$766.1778	$766.18	$766.15	$766.20