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	$75.79	12.150%	$84.9985	$85.00	$85.00	$85.00
Purchase #2	$69.75	9.197%	$76.1649	$76.16	$76.15	$76.20
Purchase #3	$32.48	13.758%	$36.9486	$36.95	$36.95	$36.90
Purchase #4	$189.86	10.550%	$209.8902	$209.89	$209.90	$209.90
Purchase #5	$204.97	8.574%	$222.5441	$222.54	$222.55	$222.50
Purchase #6	$14.97	3.214%	$15.4511	$15.45	$15.45	$15.50
Purchase #7	$112.75	13.159%	$127.5868	$127.59	$127.60	$127.60
7 purchase totals =	$700.57		$773.5842	$773.58	$773.60	$773.60