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	$78.81	8.282%	$85.337	$85.34	$85.35	$85.30
Purchase #2	$53.98	7.114%	$57.8201	$57.82	$57.80	$57.80
Purchase #3	$71.32	10.692%	$78.9455	$78.95	$78.95	$78.90
Purchase #4	$44.78	9.359%	$48.971	$48.97	$48.95	$49.00
Purchase #5	$5.94	8.812%	$6.4634	$6.46	$6.45	$6.50
Purchase #6	$168.91	6.748%	$180.308	$180.31	$180.30	$180.30
Purchase #7	$127.54	4.312%	$133.0395	$133.04	$133.05	$133.00
7 purchase totals =	$551.28		$590.8845	$590.89	$590.85	$590.80