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	$75.56	12.578%	$85.0639	$85.06	$85.05	$85.10
Purchase #2	$37.54	9.185%	$40.988	$40.99	$41.00	$41.00
Purchase #3	$31.34	13.684%	$35.6286	$35.63	$35.65	$35.60
Purchase #4	$19.31	7.845%	$20.8249	$20.82	$20.80	$20.80
Purchase #5	$40.27	5.768%	$42.5928	$42.59	$42.60	$42.60
Purchase #6	$225.69	6.746%	$240.915	$240.92	$240.90	$240.90
Purchase #7	$186.92	12.275%	$209.8644	$209.86	$209.85	$209.90
7 purchase totals =	$616.63		$675.8776	$675.87	$675.85	$675.90