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	$77.80	6.397%	$82.7769	$82.78	$82.80	$82.80
Purchase #2	$91.58	4.674%	$95.8604	$95.86	$95.85	$95.90
Purchase #3	$214.48	3.249%	$221.4485	$221.45	$221.45	$221.40
Purchase #4	$141.60	7.342%	$151.9963	$152.00	$152.00	$152.00
Purchase #5	$147.90	13.291%	$167.5574	$167.56	$167.55	$167.60
Purchase #6	$91.55	4.476%	$95.6478	$95.65	$95.65	$95.60
Purchase #7	$122.95	9.707%	$134.8848	$134.88	$134.90	$134.90
7 purchase totals =	$887.86		$950.1721	$950.18	$950.20	$950.20