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	$49.31	6.500%	$52.5152	$52.52	$52.50	$52.50
Purchase #2	$238.52	13.105%	$269.778	$269.78	$269.80	$269.80
Purchase #3	$208.46	6.584%	$222.185	$222.19	$222.20	$222.20
Purchase #4	$136.30	11.452%	$151.9091	$151.91	$151.90	$151.90
Purchase #5	$18.53	13.565%	$21.0436	$21.04	$21.05	$21.00
Purchase #6	$101.58	3.234%	$104.8651	$104.87	$104.85	$104.90
Purchase #7	$209.83	12.226%	$235.4838	$235.48	$235.50	$235.50
7 purchase totals =	$962.53		$1,057.7798	$1,057.79	$1,057.80	$1,057.80