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	$230.65	13.850%	$262.595	$262.60	$262.60	$262.60
Purchase #2	$237.32	7.512%	$255.1475	$255.15	$255.15	$255.10
Purchase #3	$103.54	11.730%	$115.6852	$115.69	$115.70	$115.70
Purchase #4	$146.58	12.496%	$164.8966	$164.90	$164.90	$164.90
Purchase #5	$50.32	13.738%	$57.233	$57.23	$57.25	$57.20
Purchase #6	$190.62	7.375%	$204.6782	$204.68	$204.70	$204.70
Purchase #7	$83.41	8.684%	$90.6533	$90.65	$90.65	$90.70
7 purchase totals =	$1,042.44		$1,150.8888	$1,150.90	$1,150.95	$1,150.90