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	$146.62	13.105%	$165.8346	$165.83	$165.85	$165.80
Purchase #2	$11.34	6.612%	$12.0898	$12.09	$12.10	$12.10
Purchase #3	$191.52	8.657%	$208.0999	$208.10	$208.10	$208.10
Purchase #4	$32.41	4.496%	$33.8672	$33.87	$33.85	$33.90
Purchase #5	$27.64	5.149%	$29.0632	$29.06	$29.05	$29.10
Purchase #6	$21.57	4.371%	$22.5128	$22.51	$22.50	$22.50
Purchase #7	$94.28	5.701%	$99.6549	$99.65	$99.65	$99.70
7 purchase totals =	$525.38		$571.1224	$571.11	$571.10	$571.20