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	$136.43	3.720%	$141.5052	$141.51	$141.50	$141.50
Purchase #2	$214.35	13.624%	$243.553	$243.55	$243.55	$243.60
Purchase #3	$32.53	6.760%	$34.729	$34.73	$34.75	$34.70
Purchase #4	$30.93	8.447%	$33.5427	$33.54	$33.55	$33.50
Purchase #5	$9.86	11.350%	$10.9791	$10.98	$11.00	$11.00
Purchase #6	$156.82	4.653%	$164.1168	$164.12	$164.10	$164.10
Purchase #7	$144.67	6.739%	$154.4193	$154.42	$154.40	$154.40
7 purchase totals =	$725.59		$782.8451	$782.85	$782.85	$782.80