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	$140.26	12.738%	$158.1263	$158.13	$158.15	$158.10
Purchase #2	$43.44	12.594%	$48.9108	$48.91	$48.90	$48.90
Purchase #3	$65.79	8.762%	$71.5545	$71.55	$71.55	$71.60
Purchase #4	$13.25	3.795%	$13.7528	$13.75	$13.75	$13.80
Purchase #5	$89.78	12.396%	$100.9091	$100.91	$100.90	$100.90
Purchase #6	$226.29	11.429%	$252.1527	$252.15	$252.15	$252.20
Purchase #7	$52.76	12.597%	$59.4062	$59.41	$59.40	$59.40
7 purchase totals =	$631.57		$704.8124	$704.81	$704.80	$704.90