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	$154.82	13.646%	$175.9467	$175.95	$175.95	$175.90
Purchase #2	$24.74	13.335%	$28.0391	$28.04	$28.05	$28.00
Purchase #3	$211.70	10.786%	$234.534	$234.53	$234.55	$234.50
Purchase #4	$248.85	13.567%	$282.6115	$282.61	$282.60	$282.60
Purchase #5	$153.78	11.501%	$171.4662	$171.47	$171.45	$171.50
Purchase #6	$206.94	8.110%	$223.7228	$223.72	$223.70	$223.70
Purchase #7	$141.95	4.606%	$148.4882	$148.49	$148.50	$148.50
7 purchase totals =	$1,142.78		$1,264.8085	$1,264.81	$1,264.80	$1,264.70