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	$136.36	12.824%	$153.8468	$153.85	$153.85	$153.80
Purchase #2	$213.37	13.405%	$241.9722	$241.97	$241.95	$242.00
Purchase #3	$80.81	7.340%	$86.7415	$86.74	$86.75	$86.70
Purchase #4	$130.56	11.699%	$145.8342	$145.83	$145.85	$145.80
Purchase #5	$161.65	5.672%	$170.8188	$170.82	$170.80	$170.80
Purchase #6	$135.27	5.547%	$142.7734	$142.77	$142.75	$142.80
Purchase #7	$95.80	3.492%	$99.1453	$99.15	$99.15	$99.10
7 purchase totals =	$953.82		$1,041.1322	$1,041.13	$1,041.10	$1,041.00