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	$217.94	13.443%	$247.2377	$247.24	$247.25	$247.20
Purchase #2	$70.98	10.129%	$78.1696	$78.17	$78.15	$78.20
Purchase #3	$146.40	6.374%	$155.7315	$155.73	$155.75	$155.70
Purchase #4	$34.40	4.153%	$35.8286	$35.83	$35.85	$35.80
Purchase #5	$244.36	7.443%	$262.5477	$262.55	$262.55	$262.50
Purchase #6	$185.51	7.713%	$199.8184	$199.82	$199.80	$199.80
Purchase #7	$45.68	11.194%	$50.7934	$50.79	$50.80	$50.80
7 purchase totals =	$945.27		$1,030.1269	$1,030.13	$1,030.15	$1,030.00