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	$98.56	7.434%	$105.887	$105.89	$105.90	$105.90
Purchase #2	$59.77	6.419%	$63.6066	$63.61	$63.60	$63.60
Purchase #3	$172.59	11.822%	$192.9936	$192.99	$193.00	$193.00
Purchase #4	$91.90	6.832%	$98.1786	$98.18	$98.20	$98.20
Purchase #5	$46.68	8.447%	$50.6231	$50.62	$50.60	$50.60
Purchase #6	$104.59	12.532%	$117.6972	$117.70	$117.70	$117.70
Purchase #7	$95.92	10.105%	$105.6127	$105.61	$105.60	$105.60
7 purchase totals =	$670.01		$734.5988	$734.60	$734.60	$734.60