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	$195.59	13.367%	$221.7345	$221.73	$221.75	$221.70
Purchase #2	$246.82	8.428%	$267.622	$267.62	$267.60	$267.60
Purchase #3	$100.61	5.192%	$105.8337	$105.83	$105.85	$105.80
Purchase #4	$83.28	4.666%	$87.1658	$87.17	$87.15	$87.20
Purchase #5	$208.56	13.392%	$236.4904	$236.49	$236.50	$236.50
Purchase #6	$38.45	7.341%	$41.2726	$41.27	$41.25	$41.30
Purchase #7	$161.25	3.624%	$167.0937	$167.09	$167.10	$167.10
7 purchase totals =	$1,034.56		$1,127.2127	$1,127.20	$1,127.20	$1,127.20