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	$109.44	3.779%	$113.5757	$113.58	$113.60	$113.60
Purchase #2	$242.85	8.180%	$262.7151	$262.72	$262.70	$262.70
Purchase #3	$212.69	10.692%	$235.4308	$235.43	$235.45	$235.40
Purchase #4	$156.43	12.447%	$175.9008	$175.90	$175.90	$175.90
Purchase #5	$23.90	4.123%	$24.8854	$24.89	$24.90	$24.90
Purchase #6	$159.28	5.151%	$167.4845	$167.48	$167.50	$167.50
Purchase #7	$25.93	10.105%	$28.5502	$28.55	$28.55	$28.60
7 purchase totals =	$930.52		$1,008.5425	$1,008.55	$1,008.60	$1,008.60