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	$69.38	13.725%	$78.9024	$78.90	$78.90	$78.90
Purchase #2	$66.47	8.544%	$72.1492	$72.15	$72.15	$72.10
Purchase #3	$47.26	11.195%	$52.5508	$52.55	$52.55	$52.60
Purchase #4	$59.39	10.457%	$65.6004	$65.60	$65.60	$65.60
Purchase #5	$51.41	11.213%	$57.1746	$57.17	$57.15	$57.20
Purchase #6	$141.55	3.780%	$146.9006	$146.90	$146.90	$146.90
Purchase #7	$250.29	7.528%	$269.1318	$269.13	$269.15	$269.10
7 purchase totals =	$685.75		$742.4098	$742.40	$742.40	$742.40