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	$82.77	3.383%	$85.5701	$85.57	$85.55	$85.60
Purchase #2	$28.78	7.734%	$31.0058	$31.01	$31.00	$31.00
Purchase #3	$186.48	12.122%	$209.0851	$209.09	$209.10	$209.10
Purchase #4	$151.29	4.767%	$158.502	$158.50	$158.50	$158.50
Purchase #5	$114.27	3.124%	$117.8398	$117.84	$117.85	$117.80
Purchase #6	$92.50	12.155%	$103.7434	$103.74	$103.75	$103.70
Purchase #7	$203.32	12.778%	$229.3002	$229.30	$229.30	$229.30
7 purchase totals =	$859.41		$935.0464	$935.05	$935.05	$935.00