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	$185.51	13.680%	$210.8878	$210.89	$210.90	$210.90
Purchase #2	$152.92	12.818%	$172.5213	$172.52	$172.50	$172.50
Purchase #3	$203.77	5.679%	$215.3421	$215.34	$215.35	$215.30
Purchase #4	$217.99	8.608%	$236.7546	$236.75	$236.75	$236.80
Purchase #5	$136.61	10.473%	$150.9172	$150.92	$150.90	$150.90
Purchase #6	$118.27	5.660%	$124.9641	$124.96	$124.95	$125.00
Purchase #7	$147.54	3.342%	$152.4708	$152.47	$152.45	$152.50
7 purchase totals =	$1,162.61		$1,263.8579	$1,263.85	$1,263.80	$1,263.90