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	$135.90	12.388%	$152.7353	$152.74	$152.75	$152.70
Purchase #2	$13.26	7.573%	$14.2642	$14.26	$14.25	$14.30
Purchase #3	$210.39	3.260%	$217.2487	$217.25	$217.25	$217.20
Purchase #4	$43.61	5.232%	$45.8917	$45.89	$45.90	$45.90
Purchase #5	$125.32	4.520%	$130.9845	$130.98	$131.00	$131.00
Purchase #6	$239.48	8.371%	$259.5269	$259.53	$259.55	$259.50
Purchase #7	$137.39	13.464%	$155.8882	$155.89	$155.90	$155.90
7 purchase totals =	$905.35		$976.5395	$976.54	$976.60	$976.50