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	$42.66	7.714%	$45.9508	$45.95	$45.95	$46.00
Purchase #2	$86.70	4.292%	$90.4212	$90.42	$90.40	$90.40
Purchase #3	$63.48	10.806%	$70.3396	$70.34	$70.35	$70.30
Purchase #4	$100.32	7.172%	$107.515	$107.52	$107.50	$107.50
Purchase #5	$153.48	12.423%	$172.5468	$172.55	$172.55	$172.50
Purchase #6	$123.95	10.853%	$137.4023	$137.40	$137.40	$137.40
Purchase #7	$37.44	11.618%	$41.7898	$41.79	$41.80	$41.80
7 purchase totals =	$608.03		$665.9655	$665.97	$665.95	$665.90