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	$119.31	6.352%	$126.8886	$126.89	$126.90	$126.90
Purchase #2	$99.61	7.363%	$106.9443	$106.94	$106.95	$106.90
Purchase #3	$233.83	7.179%	$250.6167	$250.62	$250.60	$250.60
Purchase #4	$220.38	5.795%	$233.151	$233.15	$233.15	$233.20
Purchase #5	$142.42	8.719%	$154.8376	$154.84	$154.85	$154.80
Purchase #6	$57.77	3.721%	$59.9196	$59.92	$59.90	$59.90
Purchase #7	$81.82	10.619%	$90.5085	$90.51	$90.50	$90.50
7 purchase totals =	$955.14		$1,022.8663	$1,022.87	$1,022.85	$1,022.80