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	$134.48	12.214%	$150.9054	$150.91	$150.90	$150.90
Purchase #2	$161.45	9.849%	$177.3512	$177.35	$177.35	$177.40
Purchase #3	$245.72	13.499%	$278.8897	$278.89	$278.90	$278.90
Purchase #4	$215.52	12.199%	$241.8113	$241.81	$241.80	$241.80
Purchase #5	$64.74	8.651%	$70.3407	$70.34	$70.35	$70.30
Purchase #6	$59.27	5.691%	$62.6431	$62.64	$62.65	$62.60
Purchase #7	$161.73	5.479%	$170.5912	$170.59	$170.60	$170.60
7 purchase totals =	$1,042.91		$1,152.5326	$1,152.53	$1,152.55	$1,152.50