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	$29.47	11.388%	$32.826	$32.83	$32.85	$32.80
Purchase #2	$96.79	11.707%	$108.1212	$108.12	$108.10	$108.10
Purchase #3	$213.49	11.557%	$238.163	$238.16	$238.15	$238.20
Purchase #4	$180.85	8.642%	$196.4791	$196.48	$196.50	$196.50
Purchase #5	$105.39	4.204%	$109.8206	$109.82	$109.80	$109.80
Purchase #6	$88.65	6.717%	$94.6046	$94.60	$94.60	$94.60
Purchase #7	$146.98	4.512%	$153.6117	$153.61	$153.60	$153.60
7 purchase totals =	$861.62		$933.6262	$933.62	$933.60	$933.60