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	$143.85	4.502%	$150.3261	$150.33	$150.35	$150.30
Purchase #2	$126.81	5.551%	$133.8492	$133.85	$133.85	$133.80
Purchase #3	$241.66	8.396%	$261.9498	$261.95	$261.95	$261.90
Purchase #4	$191.81	12.672%	$216.1162	$216.12	$216.10	$216.10
Purchase #5	$179.76	3.282%	$185.6597	$185.66	$185.65	$185.70
Purchase #6	$126.50	11.634%	$141.217	$141.22	$141.20	$141.20
Purchase #7	$21.45	5.147%	$22.554	$22.55	$22.55	$22.60
7 purchase totals =	$1,031.84		$1,111.6720	$1,111.68	$1,111.65	$1,111.60