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	$39.98	13.404%	$45.3389	$45.34	$45.35	$45.30
Purchase #2	$31.39	5.287%	$33.0496	$33.05	$33.05	$33.00
Purchase #3	$80.55	13.852%	$91.7078	$91.71	$91.70	$91.70
Purchase #4	$175.29	5.685%	$185.2552	$185.26	$185.25	$185.30
Purchase #5	$126.90	3.756%	$131.6664	$131.67	$131.65	$131.70
Purchase #6	$241.85	3.446%	$250.1842	$250.18	$250.20	$250.20
Purchase #7	$200.39	5.274%	$210.9586	$210.96	$210.95	$211.00
7 purchase totals =	$896.35		$948.1607	$948.17	$948.15	$948.20