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	$37.45	11.752%	$41.8511	$41.85	$41.85	$41.90
Purchase #2	$42.43	4.159%	$44.1947	$44.19	$44.20	$44.20
Purchase #3	$235.33	12.859%	$265.5911	$265.59	$265.60	$265.60
Purchase #4	$115.86	12.647%	$130.5128	$130.51	$130.50	$130.50
Purchase #5	$185.43	12.530%	$208.6644	$208.66	$208.65	$208.70
Purchase #6	$156.72	11.700%	$175.0562	$175.06	$175.05	$175.10
Purchase #7	$236.80	12.105%	$265.4646	$265.46	$265.45	$265.50
7 purchase totals =	$1,010.02		$1,131.3349	$1,131.32	$1,131.30	$1,131.50