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	$97.52	5.736%	$103.1137	$103.11	$103.10	$103.10
Purchase #2	$169.29	13.642%	$192.3845	$192.38	$192.40	$192.40
Purchase #3	$159.42	8.191%	$172.4781	$172.48	$172.50	$172.50
Purchase #4	$246.46	6.390%	$262.2088	$262.21	$262.20	$262.20
Purchase #5	$22.62	11.226%	$25.1593	$25.16	$25.15	$25.20
Purchase #6	$64.30	12.414%	$72.2822	$72.28	$72.30	$72.30
Purchase #7	$204.40	13.582%	$232.1616	$232.16	$232.15	$232.20
7 purchase totals =	$964.01		$1,059.7882	$1,059.78	$1,059.80	$1,059.90