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	$31.32	12.174%	$35.1329	$35.13	$35.15	$35.10
Purchase #2	$103.35	12.294%	$116.0558	$116.06	$116.05	$116.10
Purchase #3	$39.35	5.174%	$41.386	$41.39	$41.40	$41.40
Purchase #4	$202.59	5.273%	$213.2726	$213.27	$213.25	$213.30
Purchase #5	$152.92	10.378%	$168.79	$168.79	$168.80	$168.80
Purchase #6	$30.51	10.778%	$33.7984	$33.80	$33.80	$33.80
Purchase #7	$157.59	13.682%	$179.1515	$179.15	$179.15	$179.20
7 purchase totals =	$717.63		$787.5872	$787.59	$787.60	$787.70