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	$92.42	3.677%	$95.8183	$95.82	$95.80	$95.80
Purchase #2	$183.25	7.400%	$196.8105	$196.81	$196.80	$196.80
Purchase #3	$213.39	7.436%	$229.2577	$229.26	$229.25	$229.30
Purchase #4	$244.72	11.102%	$271.8888	$271.89	$271.90	$271.90
Purchase #5	$12.60	13.824%	$14.3418	$14.34	$14.35	$14.30
Purchase #6	$90.61	10.364%	$100.0008	$100.00	$100.00	$100.00
Purchase #7	$231.92	13.277%	$262.712	$262.71	$262.70	$262.70
7 purchase totals =	$1,068.91		$1,170.8299	$1,170.83	$1,170.80	$1,170.80