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	$100.34	5.152%	$105.5095	$105.51	$105.50	$105.50
Purchase #2	$122.82	11.312%	$136.7134	$136.71	$136.70	$136.70
Purchase #3	$100.69	13.838%	$114.6235	$114.62	$114.60	$114.60
Purchase #4	$65.84	9.107%	$71.836	$71.84	$71.85	$71.80
Purchase #5	$169.52	10.363%	$187.0874	$187.09	$187.10	$187.10
Purchase #6	$246.43	7.304%	$264.4292	$264.43	$264.45	$264.40
Purchase #7	$192.84	7.123%	$206.576	$206.58	$206.60	$206.60
7 purchase totals =	$998.48		$1,086.7750	$1,086.78	$1,086.80	$1,086.70