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	$122.38	11.547%	$136.5112	$136.51	$136.50	$136.50
Purchase #2	$40.90	3.433%	$42.3041	$42.30	$42.30	$42.30
Purchase #3	$222.86	3.551%	$230.7738	$230.77	$230.75	$230.80
Purchase #4	$30.33	5.344%	$31.9508	$31.95	$31.95	$32.00
Purchase #5	$89.97	11.644%	$100.4461	$100.45	$100.45	$100.40
Purchase #6	$105.53	10.396%	$116.5009	$116.50	$116.50	$116.50
Purchase #7	$184.42	13.797%	$209.8644	$209.86	$209.85	$209.90
7 purchase totals =	$796.39		$868.3513	$868.34	$868.30	$868.40