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	$172.63	8.450%	$187.2172	$187.22	$187.20	$187.20
Purchase #2	$225.69	13.489%	$256.1333	$256.13	$256.15	$256.10
Purchase #3	$38.76	11.471%	$43.2062	$43.21	$43.20	$43.20
Purchase #4	$122.71	6.328%	$130.4751	$130.48	$130.50	$130.50
Purchase #5	$137.64	10.846%	$152.5684	$152.57	$152.55	$152.60
Purchase #6	$171.29	10.437%	$189.1675	$189.17	$189.15	$189.20
Purchase #7	$192.63	3.575%	$199.5165	$199.52	$199.50	$199.50
7 purchase totals =	$1,061.35		$1,158.2842	$1,158.30	$1,158.25	$1,158.30