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	$61.62	4.707%	$64.5205	$64.52	$64.50	$64.50
Purchase #2	$21.49	4.439%	$22.4439	$22.44	$22.45	$22.40
Purchase #3	$228.69	5.859%	$242.0889	$242.09	$242.10	$242.10
Purchase #4	$133.80	12.514%	$150.5437	$150.54	$150.55	$150.50
Purchase #5	$102.79	11.747%	$114.8647	$114.86	$114.85	$114.90
Purchase #6	$86.45	10.496%	$95.5238	$95.52	$95.50	$95.50
Purchase #7	$172.86	3.150%	$178.3051	$178.31	$178.30	$178.30
7 purchase totals =	$807.70		$868.2906	$868.28	$868.25	$868.20