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	$64.50	11.316%	$71.7988	$71.80	$71.80	$71.80
Purchase #2	$153.28	7.539%	$164.8358	$164.84	$164.85	$164.80
Purchase #3	$189.58	10.105%	$208.7371	$208.74	$208.75	$208.70
Purchase #4	$130.81	9.144%	$142.7713	$142.77	$142.75	$142.80
Purchase #5	$128.50	9.666%	$140.9208	$140.92	$140.90	$140.90
Purchase #6	$212.54	8.352%	$230.2913	$230.29	$230.30	$230.30
Purchase #7	$157.52	9.297%	$172.1646	$172.16	$172.15	$172.20
7 purchase totals =	$1,036.73		$1,131.5197	$1,131.52	$1,131.50	$1,131.50