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	$48.67	4.233%	$50.7302	$50.73	$50.75	$50.70
Purchase #2	$160.59	7.207%	$172.1637	$172.16	$172.15	$172.20
Purchase #3	$217.67	8.650%	$236.4985	$236.50	$236.50	$236.50
Purchase #4	$250.83	3.191%	$258.834	$258.83	$258.85	$258.80
Purchase #5	$53.35	3.193%	$55.0535	$55.05	$55.05	$55.10
Purchase #6	$224.98	13.727%	$255.863	$255.86	$255.85	$255.90
Purchase #7	$240.60	7.752%	$259.2513	$259.25	$259.25	$259.30
7 purchase totals =	$1,196.69		$1,288.3942	$1,288.38	$1,288.40	$1,288.50