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	$223.78	4.388%	$233.5995	$233.60	$233.60	$233.60
Purchase #2	$92.89	7.285%	$99.657	$99.66	$99.65	$99.70
Purchase #3	$103.98	8.327%	$112.6384	$112.64	$112.65	$112.60
Purchase #4	$220.87	13.486%	$250.6565	$250.66	$250.65	$250.70
Purchase #5	$32.52	12.682%	$36.6442	$36.64	$36.65	$36.60
Purchase #6	$73.68	3.303%	$76.1137	$76.11	$76.10	$76.10
Purchase #7	$101.26	4.202%	$105.5149	$105.51	$105.50	$105.50
7 purchase totals =	$848.98		$914.8242	$914.82	$914.80	$914.80