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	$32.26	3.547%	$33.4043	$33.40	$33.40	$33.40
Purchase #2	$197.69	8.705%	$214.8989	$214.90	$214.90	$214.90
Purchase #3	$139.31	6.604%	$148.51	$148.51	$148.50	$148.50
Purchase #4	$197.86	9.198%	$216.0592	$216.06	$216.05	$216.10
Purchase #5	$85.28	9.577%	$93.4473	$93.45	$93.45	$93.40
Purchase #6	$138.43	12.620%	$155.8999	$155.90	$155.90	$155.90
Purchase #7	$139.39	5.419%	$146.9435	$146.94	$146.95	$146.90
7 purchase totals =	$930.22		$1,009.1631	$1,009.16	$1,009.15	$1,009.10