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	$196.82	13.216%	$222.8317	$222.83	$222.85	$222.80
Purchase #2	$89.83	7.871%	$96.9005	$96.90	$96.90	$96.90
Purchase #3	$233.83	10.572%	$258.5505	$258.55	$258.55	$258.60
Purchase #4	$76.49	3.176%	$78.9193	$78.92	$78.90	$78.90
Purchase #5	$245.61	8.705%	$266.9904	$266.99	$267.00	$267.00
Purchase #6	$139.83	8.354%	$151.5114	$151.51	$151.50	$151.50
Purchase #7	$243.52	5.336%	$256.5142	$256.51	$256.50	$256.50
7 purchase totals =	$1,225.93		$1,332.2180	$1,332.21	$1,332.20	$1,332.20