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	$127.58	7.268%	$136.8525	$136.85	$136.85	$136.90
Purchase #2	$196.25	12.675%	$221.1247	$221.12	$221.10	$221.10
Purchase #3	$141.69	5.706%	$149.7748	$149.77	$149.75	$149.80
Purchase #4	$44.29	7.555%	$47.6361	$47.64	$47.65	$47.60
Purchase #5	$50.56	5.491%	$53.3362	$53.34	$53.35	$53.30
Purchase #6	$180.31	11.430%	$200.9194	$200.92	$200.90	$200.90
Purchase #7	$199.67	11.240%	$222.1129	$222.11	$222.10	$222.10
7 purchase totals =	$940.35		$1,031.7566	$1,031.75	$1,031.70	$1,031.70