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	$214.71	13.295%	$243.2557	$243.26	$243.25	$243.30
Purchase #2	$14.33	10.847%	$15.8844	$15.88	$15.90	$15.90
Purchase #3	$185.41	8.327%	$200.8491	$200.85	$200.85	$200.80
Purchase #4	$43.33	7.358%	$46.5182	$46.52	$46.50	$46.50
Purchase #5	$18.61	6.390%	$19.7992	$19.80	$19.80	$19.80
Purchase #6	$175.72	7.831%	$189.4806	$189.48	$189.50	$189.50
Purchase #7	$181.27	10.727%	$200.7148	$200.71	$200.70	$200.70
7 purchase totals =	$833.38		$916.5020	$916.50	$916.50	$916.50