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	$147.28	4.443%	$153.8237	$153.82	$153.80	$153.80
Purchase #2	$195.75	11.442%	$218.1477	$218.15	$218.15	$218.10
Purchase #3	$112.76	10.428%	$124.5186	$124.52	$124.50	$124.50
Purchase #4	$59.85	13.149%	$67.7197	$67.72	$67.70	$67.70
Purchase #5	$39.93	11.568%	$44.5491	$44.55	$44.55	$44.50
Purchase #6	$93.57	12.451%	$105.2204	$105.22	$105.20	$105.20
Purchase #7	$203.76	4.805%	$213.5507	$213.55	$213.55	$213.60
7 purchase totals =	$852.90		$927.5299	$927.53	$927.45	$927.40