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	$58.37	7.766%	$62.903	$62.90	$62.90	$62.90
Purchase #2	$138.31	5.500%	$145.9171	$145.92	$145.90	$145.90
Purchase #3	$97.39	7.860%	$105.0449	$105.04	$105.05	$105.00
Purchase #4	$61.92	5.334%	$65.2228	$65.22	$65.20	$65.20
Purchase #5	$6.95	12.499%	$7.8187	$7.82	$7.80	$7.80
Purchase #6	$161.61	3.241%	$166.8478	$166.85	$166.85	$166.80
Purchase #7	$50.39	10.615%	$55.7389	$55.74	$55.75	$55.70
7 purchase totals =	$574.94		$609.4932	$609.49	$609.45	$609.30