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	$129.83	11.275%	$144.4683	$144.47	$144.45	$144.50
Purchase #2	$200.94	12.391%	$225.8385	$225.84	$225.85	$225.80
Purchase #3	$232.73	13.826%	$264.9072	$264.91	$264.90	$264.90
Purchase #4	$113.53	4.220%	$118.321	$118.32	$118.30	$118.30
Purchase #5	$10.44	10.327%	$11.5181	$11.52	$11.50	$11.50
Purchase #6	$216.27	4.404%	$225.7945	$225.79	$225.80	$225.80
Purchase #7	$129.66	8.873%	$141.1647	$141.16	$141.15	$141.20
7 purchase totals =	$1,033.40		$1,132.0123	$1,132.01	$1,131.95	$1,132.00