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	$124.47	13.149%	$140.8366	$140.84	$140.85	$140.80
Purchase #2	$74.34	11.623%	$82.9805	$82.98	$83.00	$83.00
Purchase #3	$169.49	3.436%	$175.3137	$175.31	$175.30	$175.30
Purchase #4	$81.69	9.232%	$89.2316	$89.23	$89.25	$89.20
Purchase #5	$78.42	4.635%	$82.0548	$82.05	$82.05	$82.10
Purchase #6	$208.64	8.114%	$225.569	$225.57	$225.55	$225.60
Purchase #7	$33.30	6.210%	$35.3679	$35.37	$35.35	$35.40
7 purchase totals =	$770.35		$831.3541	$831.35	$831.35	$831.40