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	$113.64	7.725%	$122.4187	$122.42	$122.40	$122.40
Purchase #2	$136.90	5.536%	$144.4788	$144.48	$144.50	$144.50
Purchase #3	$134.62	12.850%	$151.9187	$151.92	$151.90	$151.90
Purchase #4	$141.54	9.530%	$155.0288	$155.03	$155.05	$155.00
Purchase #5	$128.61	8.317%	$139.3065	$139.31	$139.30	$139.30
Purchase #6	$186.67	5.324%	$196.6083	$196.61	$196.60	$196.60
Purchase #7	$157.75	13.568%	$179.1535	$179.15	$179.15	$179.20
7 purchase totals =	$999.73		$1,088.9133	$1,088.92	$1,088.90	$1,088.90