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	$81.78	10.694%	$90.5256	$90.53	$90.55	$90.50
Purchase #2	$164.29	3.785%	$170.5084	$170.51	$170.50	$170.50
Purchase #3	$175.90	13.462%	$199.5797	$199.58	$199.60	$199.60
Purchase #4	$38.32	11.838%	$42.8563	$42.86	$42.85	$42.90
Purchase #5	$194.34	7.251%	$208.4316	$208.43	$208.45	$208.40
Purchase #6	$153.98	5.550%	$162.5259	$162.53	$162.55	$162.50
Purchase #7	$148.47	7.863%	$160.1442	$160.14	$160.15	$160.10
7 purchase totals =	$957.08		$1,034.5717	$1,034.58	$1,034.65	$1,034.50