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	$39.59	13.462%	$44.9196	$44.92	$44.90	$44.90
Purchase #2	$20.37	4.338%	$21.2537	$21.25	$21.25	$21.30
Purchase #3	$52.78	4.297%	$55.048	$55.05	$55.05	$55.00
Purchase #4	$76.37	9.374%	$83.5289	$83.53	$83.55	$83.50
Purchase #5	$86.89	12.205%	$97.4949	$97.49	$97.50	$97.50
Purchase #6	$141.89	12.666%	$159.8618	$159.86	$159.85	$159.90
Purchase #7	$137.56	5.584%	$145.2414	$145.24	$145.25	$145.20
7 purchase totals =	$555.45		$607.3483	$607.34	$607.35	$607.30