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	$234.77	7.276%	$251.8519	$251.85	$251.85	$251.90
Purchase #2	$6.64	7.443%	$7.1342	$7.13	$7.15	$7.10
Purchase #3	$206.94	7.572%	$222.6095	$222.61	$222.60	$222.60
Purchase #4	$90.33	11.110%	$100.3657	$100.37	$100.35	$100.40
Purchase #5	$54.49	13.243%	$61.7061	$61.71	$61.70	$61.70
Purchase #6	$139.40	12.642%	$157.0229	$157.02	$157.00	$157.00
Purchase #7	$140.82	4.547%	$147.2231	$147.22	$147.20	$147.20
7 purchase totals =	$873.39		$947.9134	$947.91	$947.85	$947.90