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	$175.67	9.563%	$192.4693	$192.47	$192.45	$192.50
Purchase #2	$37.41	6.363%	$39.7904	$39.79	$39.80	$39.80
Purchase #3	$221.80	6.309%	$235.7934	$235.79	$235.80	$235.80
Purchase #4	$63.27	6.480%	$67.3699	$67.37	$67.35	$67.40
Purchase #5	$82.27	9.397%	$90.0009	$90.00	$90.00	$90.00
Purchase #6	$139.28	9.130%	$151.9963	$152.00	$152.00	$152.00
Purchase #7	$214.96	12.335%	$241.4753	$241.48	$241.50	$241.50
7 purchase totals =	$934.66		$1,018.8955	$1,018.90	$1,018.90	$1,019.00