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	$37.90	9.420%	$41.4702	$41.47	$41.45	$41.50
Purchase #2	$50.44	3.221%	$52.0647	$52.06	$52.05	$52.10
Purchase #3	$18.54	13.798%	$21.0981	$21.10	$21.10	$21.10
Purchase #4	$30.79	7.468%	$33.0894	$33.09	$33.10	$33.10
Purchase #5	$140.67	8.579%	$152.7381	$152.74	$152.75	$152.70
Purchase #6	$37.35	3.175%	$38.5359	$38.54	$38.55	$38.50
Purchase #7	$87.77	5.709%	$92.7808	$92.78	$92.80	$92.80
7 purchase totals =	$403.46		$431.7772	$431.78	$431.80	$431.80