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	$197.27	13.273%	$223.4536	$223.45	$223.45	$223.50
Purchase #2	$94.92	11.155%	$105.5083	$105.51	$105.50	$105.50
Purchase #3	$10.98	7.497%	$11.8032	$11.80	$11.80	$11.80
Purchase #4	$35.88	10.691%	$39.7159	$39.72	$39.70	$39.70
Purchase #5	$168.54	7.271%	$180.7945	$180.79	$180.80	$180.80
Purchase #6	$93.80	8.198%	$101.4897	$101.49	$101.50	$101.50
Purchase #7	$17.86	11.173%	$19.8555	$19.86	$19.85	$19.90
7 purchase totals =	$619.25		$682.6207	$682.62	$682.60	$682.70