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	$172.36	12.847%	$194.5031	$194.50	$194.50	$194.50
Purchase #2	$221.89	5.297%	$233.6435	$233.64	$233.65	$233.60
Purchase #3	$131.69	11.620%	$146.9924	$146.99	$147.00	$147.00
Purchase #4	$164.56	10.706%	$182.1778	$182.18	$182.20	$182.20
Purchase #5	$34.71	3.244%	$35.836	$35.84	$35.85	$35.80
Purchase #6	$141.55	7.775%	$152.5555	$152.56	$152.55	$152.60
Purchase #7	$50.64	12.227%	$56.8318	$56.83	$56.85	$56.80
7 purchase totals =	$917.40		$1,002.5401	$1,002.54	$1,002.60	$1,002.50