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	$144.35	6.658%	$153.9608	$153.96	$153.95	$154.00
Purchase #2	$12.26	4.712%	$12.8377	$12.84	$12.85	$12.80
Purchase #3	$99.67	3.485%	$103.1435	$103.14	$103.15	$103.10
Purchase #4	$180.93	8.501%	$196.3109	$196.31	$196.30	$196.30
Purchase #5	$188.47	6.541%	$200.7978	$200.80	$200.80	$200.80
Purchase #6	$130.57	13.557%	$148.2714	$148.27	$148.25	$148.30
Purchase #7	$239.47	6.417%	$254.8368	$254.84	$254.85	$254.80
7 purchase totals =	$995.72		$1,070.1589	$1,070.16	$1,070.15	$1,070.10