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	$109.47	3.738%	$113.562	$113.56	$113.55	$113.60
Purchase #2	$17.45	12.214%	$19.5813	$19.58	$19.60	$19.60
Purchase #3	$204.47	13.290%	$231.6441	$231.64	$231.65	$231.60
Purchase #4	$250.53	6.733%	$267.3982	$267.40	$267.40	$267.40
Purchase #5	$123.95	10.205%	$136.5991	$136.60	$136.60	$136.60
Purchase #6	$209.70	13.594%	$238.2066	$238.21	$238.20	$238.20
Purchase #7	$80.86	10.479%	$89.3333	$89.33	$89.35	$89.30
7 purchase totals =	$996.43		$1,096.3246	$1,096.32	$1,096.35	$1,096.30