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	$123.62	7.565%	$132.9719	$132.97	$132.95	$133.00
Purchase #2	$87.48	7.103%	$93.6937	$93.69	$93.70	$93.70
Purchase #3	$123.33	6.810%	$131.7288	$131.73	$131.75	$131.70
Purchase #4	$165.73	3.532%	$171.5836	$171.58	$171.60	$171.60
Purchase #5	$150.81	11.504%	$168.1592	$168.16	$168.15	$168.20
Purchase #6	$110.48	8.167%	$119.5029	$119.50	$119.50	$119.50
Purchase #7	$176.59	12.869%	$199.3154	$199.32	$199.30	$199.30
7 purchase totals =	$938.04		$1,016.9555	$1,016.95	$1,016.95	$1,017.00