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	$106.50	11.112%	$118.3343	$118.33	$118.35	$118.30
Purchase #2	$185.93	4.762%	$194.784	$194.78	$194.80	$194.80
Purchase #3	$143.89	3.321%	$148.6686	$148.67	$148.65	$148.70
Purchase #4	$169.66	13.468%	$192.5098	$192.51	$192.50	$192.50
Purchase #5	$249.50	11.631%	$278.5193	$278.52	$278.50	$278.50
Purchase #6	$86.53	10.830%	$95.9012	$95.90	$95.90	$95.90
Purchase #7	$171.53	4.660%	$179.5233	$179.52	$179.50	$179.50
7 purchase totals =	$1,113.54		$1,208.2405	$1,208.23	$1,208.20	$1,208.20