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	$106.61	5.708%	$112.6953	$112.70	$112.70	$112.70
Purchase #2	$152.60	11.666%	$170.4023	$170.40	$170.40	$170.40
Purchase #3	$151.80	10.446%	$167.657	$167.66	$167.65	$167.70
Purchase #4	$216.45	11.665%	$241.6989	$241.70	$241.70	$241.70
Purchase #5	$85.85	4.786%	$89.9588	$89.96	$89.95	$90.00
Purchase #6	$34.82	8.813%	$37.8887	$37.89	$37.90	$37.90
Purchase #7	$248.80	7.199%	$266.7111	$266.71	$266.70	$266.70
7 purchase totals =	$996.93		$1,087.0121	$1,087.02	$1,087.00	$1,087.10