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	$78.53	6.167%	$83.3729	$83.37	$83.35	$83.40
Purchase #2	$29.36	7.843%	$31.6627	$31.66	$31.65	$31.70
Purchase #3	$58.42	6.147%	$62.0111	$62.01	$62.00	$62.00
Purchase #4	$127.84	7.793%	$137.8026	$137.80	$137.80	$137.80
Purchase #5	$62.49	6.167%	$66.3438	$66.34	$66.35	$66.30
Purchase #6	$43.32	5.638%	$45.7624	$45.76	$45.75	$45.80
Purchase #7	$198.36	11.691%	$221.5503	$221.55	$221.55	$221.60
7 purchase totals =	$598.32		$648.5058	$648.49	$648.45	$648.60