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	$144.67	13.815%	$164.6562	$164.66	$164.65	$164.70
Purchase #2	$119.28	10.562%	$131.8784	$131.88	$131.90	$131.90
Purchase #3	$30.81	10.838%	$34.1492	$34.15	$34.15	$34.10
Purchase #4	$87.58	8.273%	$94.8255	$94.83	$94.85	$94.80
Purchase #5	$36.61	3.617%	$37.9342	$37.93	$37.95	$37.90
Purchase #6	$82.58	3.510%	$85.4786	$85.48	$85.50	$85.50
Purchase #7	$138.81	13.321%	$157.3009	$157.30	$157.30	$157.30
7 purchase totals =	$640.34		$706.2230	$706.23	$706.30	$706.20