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	$164.50	12.678%	$185.3553	$185.36	$185.35	$185.40
Purchase #2	$91.45	8.315%	$99.0541	$99.05	$99.05	$99.10
Purchase #3	$57.53	5.727%	$60.8247	$60.82	$60.80	$60.80
Purchase #4	$112.98	11.741%	$126.245	$126.25	$126.25	$126.20
Purchase #5	$188.82	4.396%	$197.1205	$197.12	$197.10	$197.10
Purchase #6	$145.43	13.318%	$164.7984	$164.80	$164.80	$164.80
Purchase #7	$94.66	5.388%	$99.7603	$99.76	$99.75	$99.80
7 purchase totals =	$855.37		$933.1583	$933.16	$933.10	$933.20