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	$63.83	3.339%	$65.9613	$65.96	$65.95	$66.00
Purchase #2	$72.73	4.870%	$76.272	$76.27	$76.25	$76.30
Purchase #3	$10.43	10.819%	$11.5584	$11.56	$11.55	$11.60
Purchase #4	$162.66	13.800%	$185.1071	$185.11	$185.10	$185.10
Purchase #5	$132.88	7.217%	$142.4699	$142.47	$142.45	$142.50
Purchase #6	$217.87	11.716%	$243.3956	$243.40	$243.40	$243.40
Purchase #7	$153.38	13.122%	$173.5065	$173.51	$173.50	$173.50
7 purchase totals =	$813.78		$898.2708	$898.28	$898.20	$898.40