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	$99.54	5.653%	$105.167	$105.17	$105.15	$105.20
Purchase #2	$85.81	11.560%	$95.7296	$95.73	$95.75	$95.70
Purchase #3	$197.68	5.462%	$208.4773	$208.48	$208.50	$208.50
Purchase #4	$84.94	11.566%	$94.7642	$94.76	$94.75	$94.80
Purchase #5	$59.71	9.846%	$65.589	$65.59	$65.60	$65.60
Purchase #6	$107.41	11.237%	$119.4797	$119.48	$119.50	$119.50
Purchase #7	$58.55	12.167%	$65.6738	$65.67	$65.65	$65.70
7 purchase totals =	$693.64		$754.8806	$754.88	$754.90	$755.00