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	$175.41	3.671%	$181.8493	$181.85	$181.85	$181.80
Purchase #2	$27.30	9.428%	$29.8738	$29.87	$29.85	$29.90
Purchase #3	$151.91	5.256%	$159.8944	$159.89	$159.90	$159.90
Purchase #4	$147.30	7.644%	$158.5596	$158.56	$158.55	$158.60
Purchase #5	$23.79	3.633%	$24.6543	$24.65	$24.65	$24.70
Purchase #6	$48.57	11.417%	$54.1152	$54.12	$54.10	$54.10
Purchase #7	$37.78	5.393%	$39.8175	$39.82	$39.80	$39.80
7 purchase totals =	$612.06		$648.7641	$648.76	$648.70	$648.80