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	$75.53	13.688%	$85.8685	$85.87	$85.85	$85.90
Purchase #2	$74.58	10.283%	$82.2491	$82.25	$82.25	$82.20
Purchase #3	$197.39	8.497%	$214.1622	$214.16	$214.15	$214.20
Purchase #4	$32.93	6.658%	$35.1225	$35.12	$35.10	$35.10
Purchase #5	$75.82	13.642%	$86.1634	$86.16	$86.15	$86.20
Purchase #6	$32.83	8.828%	$35.7282	$35.73	$35.75	$35.70
Purchase #7	$83.28	7.275%	$89.3386	$89.34	$89.35	$89.30
7 purchase totals =	$572.36		$628.6325	$628.63	$628.60	$628.60