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	$136.47	11.233%	$151.7997	$151.80	$151.80	$151.80
Purchase #2	$50.91	4.385%	$53.1424	$53.14	$53.15	$53.10
Purchase #3	$160.80	3.170%	$165.8974	$165.90	$165.90	$165.90
Purchase #4	$44.76	12.590%	$50.3953	$50.40	$50.40	$50.40
Purchase #5	$164.52	10.610%	$181.9756	$181.98	$182.00	$182.00
Purchase #6	$246.41	10.344%	$271.8987	$271.90	$271.90	$271.90
Purchase #7	$146.65	6.539%	$156.2394	$156.24	$156.25	$156.20
7 purchase totals =	$950.52		$1,031.3485	$1,031.36	$1,031.40	$1,031.30