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	$207.89	3.210%	$214.5633	$214.56	$214.55	$214.60
Purchase #2	$86.30	9.634%	$94.6141	$94.61	$94.60	$94.60
Purchase #3	$10.33	5.421%	$10.89	$10.89	$10.90	$10.90
Purchase #4	$54.62	9.398%	$59.7532	$59.75	$59.75	$59.80
Purchase #5	$10.67	7.774%	$11.4995	$11.50	$11.50	$11.50
Purchase #6	$136.57	13.128%	$154.4989	$154.50	$154.50	$154.50
Purchase #7	$218.35	7.459%	$234.6367	$234.64	$234.65	$234.60
7 purchase totals =	$724.73		$780.4557	$780.45	$780.45	$780.50