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	$152.35	8.707%	$165.6151	$165.62	$165.60	$165.60
Purchase #2	$225.93	8.526%	$245.1928	$245.19	$245.20	$245.20
Purchase #3	$26.68	4.489%	$27.8777	$27.88	$27.90	$27.90
Purchase #4	$247.38	3.720%	$256.5825	$256.58	$256.60	$256.60
Purchase #5	$29.78	7.617%	$32.0483	$32.05	$32.05	$32.00
Purchase #6	$176.73	7.810%	$190.5326	$190.53	$190.55	$190.50
Purchase #7	$78.27	8.664%	$85.0513	$85.05	$85.05	$85.10
7 purchase totals =	$937.12		$1,002.9003	$1,002.90	$1,002.95	$1,002.90