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	$212.52	4.545%	$222.179	$222.18	$222.20	$222.20
Purchase #2	$63.97	12.281%	$71.8262	$71.83	$71.85	$71.80
Purchase #3	$142.35	4.187%	$148.3102	$148.31	$148.30	$148.30
Purchase #4	$162.82	13.179%	$184.278	$184.28	$184.30	$184.30
Purchase #5	$164.70	8.313%	$178.3915	$178.39	$178.40	$178.40
Purchase #6	$45.49	6.581%	$48.4837	$48.48	$48.50	$48.50
Purchase #7	$56.86	10.781%	$62.9901	$62.99	$63.00	$63.00
7 purchase totals =	$848.71		$916.4587	$916.46	$916.55	$916.50