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	$146.35	3.512%	$151.4898	$151.49	$151.50	$151.50
Purchase #2	$218.38	4.633%	$228.4975	$228.50	$228.50	$228.50
Purchase #3	$128.76	12.131%	$144.3799	$144.38	$144.40	$144.40
Purchase #4	$39.29	8.438%	$42.6053	$42.61	$42.60	$42.60
Purchase #5	$136.40	5.480%	$143.8747	$143.87	$143.85	$143.90
Purchase #6	$62.60	9.516%	$68.557	$68.56	$68.55	$68.60
Purchase #7	$98.47	11.495%	$109.7891	$109.79	$109.80	$109.80
7 purchase totals =	$830.25		$889.1933	$889.20	$889.20	$889.30