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	$244.77	8.221%	$264.8925	$264.89	$264.90	$264.90
Purchase #2	$119.45	3.388%	$123.497	$123.50	$123.50	$123.50
Purchase #3	$33.53	6.784%	$35.8047	$35.80	$35.80	$35.80
Purchase #4	$24.84	11.644%	$27.7324	$27.73	$27.75	$27.70
Purchase #5	$239.29	5.510%	$252.4749	$252.47	$252.45	$252.50
Purchase #6	$219.47	10.779%	$243.1267	$243.13	$243.15	$243.10
Purchase #7	$127.77	7.228%	$137.0052	$137.01	$137.00	$137.00
7 purchase totals =	$1,009.12		$1,084.5334	$1,084.53	$1,084.55	$1,084.50