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	$66.33	11.490%	$73.9513	$73.95	$73.95	$74.00
Purchase #2	$179.27	7.406%	$192.5467	$192.55	$192.55	$192.50
Purchase #3	$234.32	9.614%	$256.8475	$256.85	$256.85	$256.80
Purchase #4	$34.35	10.380%	$37.9155	$37.92	$37.90	$37.90
Purchase #5	$167.43	3.188%	$172.7677	$172.77	$172.75	$172.80
Purchase #6	$44.51	13.259%	$50.4116	$50.41	$50.40	$50.40
Purchase #7	$139.94	13.676%	$159.0782	$159.08	$159.10	$159.10
7 purchase totals =	$866.15		$943.5185	$943.53	$943.50	$943.50