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	$172.58	13.758%	$196.3236	$196.32	$196.30	$196.30
Purchase #2	$225.51	8.449%	$244.5633	$244.56	$244.55	$244.60
Purchase #3	$177.91	6.812%	$190.0292	$190.03	$190.05	$190.00
Purchase #4	$75.62	9.324%	$82.6708	$82.67	$82.65	$82.70
Purchase #5	$39.43	10.716%	$43.6553	$43.66	$43.65	$43.70
Purchase #6	$41.70	10.122%	$45.9209	$45.92	$45.90	$45.90
Purchase #7	$241.96	7.592%	$260.3296	$260.33	$260.35	$260.30
7 purchase totals =	$974.71		$1,063.4927	$1,063.49	$1,063.45	$1,063.50