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	$103.37	11.831%	$115.5997	$115.60	$115.60	$115.60
Purchase #2	$225.78	13.319%	$255.8516	$255.85	$255.85	$255.90
Purchase #3	$21.81	4.343%	$22.7572	$22.76	$22.75	$22.80
Purchase #4	$242.90	4.249%	$253.2208	$253.22	$253.20	$253.20
Purchase #5	$172.82	10.801%	$191.4863	$191.49	$191.50	$191.50
Purchase #6	$139.78	9.381%	$152.8928	$152.89	$152.90	$152.90
Purchase #7	$119.35	12.741%	$134.5564	$134.56	$134.55	$134.60
7 purchase totals =	$1,025.81		$1,126.3648	$1,126.37	$1,126.35	$1,126.50