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	$80.59	5.737%	$85.2134	$85.21	$85.20	$85.20
Purchase #2	$26.84	10.505%	$29.6595	$29.66	$29.65	$29.70
Purchase #3	$216.32	3.205%	$223.2531	$223.25	$223.25	$223.30
Purchase #4	$209.69	3.485%	$216.9977	$217.00	$217.00	$217.00
Purchase #5	$87.33	9.778%	$95.8691	$95.87	$95.85	$95.90
Purchase #6	$178.81	7.108%	$191.5198	$191.52	$191.50	$191.50
Purchase #7	$232.89	9.753%	$255.6038	$255.60	$255.60	$255.60
7 purchase totals =	$1,032.47		$1,098.1164	$1,098.11	$1,098.05	$1,098.20