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	$100.70	10.623%	$111.3974	$111.40	$111.40	$111.40
Purchase #2	$44.79	3.151%	$46.2013	$46.20	$46.20	$46.20
Purchase #3	$125.98	8.193%	$136.3015	$136.30	$136.30	$136.30
Purchase #4	$209.25	3.291%	$216.1364	$216.14	$216.15	$216.10
Purchase #5	$190.46	5.207%	$200.3773	$200.38	$200.40	$200.40
Purchase #6	$210.25	5.680%	$222.1922	$222.19	$222.20	$222.20
Purchase #7	$45.80	10.634%	$50.6704	$50.67	$50.65	$50.70
7 purchase totals =	$927.23		$983.2765	$983.28	$983.30	$983.30