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	$146.66	8.233%	$158.7345	$158.73	$158.75	$158.70
Purchase #2	$147.46	3.195%	$152.1713	$152.17	$152.15	$152.20
Purchase #3	$191.90	11.171%	$213.3371	$213.34	$213.35	$213.30
Purchase #4	$199.59	13.161%	$225.858	$225.86	$225.85	$225.90
Purchase #5	$19.25	7.542%	$20.7018	$20.70	$20.70	$20.70
Purchase #6	$192.46	7.249%	$206.4114	$206.41	$206.40	$206.40
Purchase #7	$95.38	5.277%	$100.4132	$100.41	$100.40	$100.40
7 purchase totals =	$992.70		$1,077.6273	$1,077.62	$1,077.60	$1,077.60