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	$238.65	5.111%	$250.8474	$250.85	$250.85	$250.80
Purchase #2	$154.49	3.236%	$159.4893	$159.49	$159.50	$159.50
Purchase #3	$213.89	3.114%	$220.5505	$220.55	$220.55	$220.60
Purchase #4	$139.89	9.229%	$152.8004	$152.80	$152.80	$152.80
Purchase #5	$140.67	9.144%	$153.5329	$153.53	$153.55	$153.50
Purchase #6	$57.73	4.607%	$60.3896	$60.39	$60.40	$60.40
Purchase #7	$141.57	13.358%	$160.4809	$160.48	$160.50	$160.50
7 purchase totals =	$1,086.89		$1,158.0910	$1,158.09	$1,158.15	$1,158.10