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	$207.87	7.681%	$223.8365	$223.84	$223.85	$223.80
Purchase #2	$39.79	11.733%	$44.4586	$44.46	$44.45	$44.50
Purchase #3	$103.48	4.813%	$108.4605	$108.46	$108.45	$108.50
Purchase #4	$181.85	13.606%	$206.5925	$206.59	$206.60	$206.60
Purchase #5	$249.57	6.456%	$265.6822	$265.68	$265.70	$265.70
Purchase #6	$54.31	9.816%	$59.6411	$59.64	$59.65	$59.60
Purchase #7	$37.89	5.330%	$39.9095	$39.91	$39.90	$39.90
7 purchase totals =	$874.76		$948.5809	$948.58	$948.60	$948.60