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	$75.38	10.460%	$83.2647	$83.26	$83.25	$83.30
Purchase #2	$119.36	10.522%	$131.9191	$131.92	$131.90	$131.90
Purchase #3	$139.87	11.355%	$155.7522	$155.75	$155.75	$155.80
Purchase #4	$42.46	6.281%	$45.1269	$45.13	$45.15	$45.10
Purchase #5	$35.75	5.491%	$37.713	$37.71	$37.70	$37.70
Purchase #6	$117.66	3.238%	$121.4698	$121.47	$121.45	$121.50
Purchase #7	$148.98	12.650%	$167.826	$167.83	$167.85	$167.80
7 purchase totals =	$679.46		$743.0717	$743.07	$743.05	$743.10