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	$32.82	13.458%	$37.2369	$37.24	$37.25	$37.20
Purchase #2	$134.52	3.445%	$139.1542	$139.15	$139.15	$139.20
Purchase #3	$45.63	5.306%	$48.0511	$48.05	$48.05	$48.10
Purchase #4	$73.85	11.318%	$82.2083	$82.21	$82.20	$82.20
Purchase #5	$133.77	13.309%	$151.5734	$151.57	$151.55	$151.60
Purchase #6	$214.92	10.816%	$238.1657	$238.17	$238.15	$238.20
Purchase #7	$47.29	6.643%	$50.4315	$50.43	$50.45	$50.40
7 purchase totals =	$682.80		$746.8211	$746.82	$746.80	$746.90