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	$129.83	11.742%	$145.0746	$145.07	$145.05	$145.10
Purchase #2	$155.63	5.637%	$164.4029	$164.40	$164.40	$164.40
Purchase #3	$198.66	11.836%	$222.1734	$222.17	$222.15	$222.20
Purchase #4	$94.51	7.370%	$101.4754	$101.48	$101.50	$101.50
Purchase #5	$127.97	13.348%	$145.0514	$145.05	$145.05	$145.10
Purchase #6	$157.35	9.518%	$172.3266	$172.33	$172.35	$172.30
Purchase #7	$40.87	11.146%	$45.4254	$45.43	$45.45	$45.40
7 purchase totals =	$904.82		$995.9297	$995.93	$995.95	$996.00