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	$131.89	11.233%	$146.7052	$146.71	$146.70	$146.70
Purchase #2	$153.75	11.537%	$171.4881	$171.49	$171.50	$171.50
Purchase #3	$100.69	12.691%	$113.4686	$113.47	$113.45	$113.50
Purchase #4	$209.31	7.257%	$224.4996	$224.50	$224.50	$224.50
Purchase #5	$134.73	11.287%	$149.937	$149.94	$149.95	$149.90
Purchase #6	$111.29	11.700%	$124.3109	$124.31	$124.30	$124.30
Purchase #7	$102.25	10.304%	$112.7858	$112.79	$112.80	$112.80
7 purchase totals =	$943.91		$1,043.1952	$1,043.21	$1,043.20	$1,043.20