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	$144.45	6.295%	$153.5431	$153.54	$153.55	$153.50
Purchase #2	$37.83	12.381%	$42.5137	$42.51	$42.50	$42.50
Purchase #3	$127.53	11.324%	$141.9715	$141.97	$141.95	$142.00
Purchase #4	$175.80	13.809%	$200.0762	$200.08	$200.10	$200.10
Purchase #5	$61.35	5.228%	$64.5574	$64.56	$64.55	$64.60
Purchase #6	$37.72	7.702%	$40.6252	$40.63	$40.65	$40.60
Purchase #7	$78.55	6.862%	$83.9401	$83.94	$83.95	$83.90
7 purchase totals =	$663.23		$727.2272	$727.23	$727.25	$727.20