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	$74.73	13.766%	$85.0173	$85.02	$85.00	$85.00
Purchase #2	$133.66	10.430%	$147.6007	$147.60	$147.60	$147.60
Purchase #3	$65.99	7.368%	$70.8521	$70.85	$70.85	$70.90
Purchase #4	$93.83	11.449%	$104.5726	$104.57	$104.55	$104.60
Purchase #5	$10.82	7.192%	$11.5982	$11.60	$11.60	$11.60
Purchase #6	$155.37	6.378%	$165.2795	$165.28	$165.30	$165.30
Purchase #7	$37.59	13.517%	$42.671	$42.67	$42.65	$42.70
7 purchase totals =	$571.99		$627.5914	$627.59	$627.55	$627.70