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	$149.67	6.292%	$159.0872	$159.09	$159.10	$159.10
Purchase #2	$67.63	5.176%	$71.1305	$71.13	$71.15	$71.10
Purchase #3	$153.81	11.205%	$171.0444	$171.04	$171.05	$171.00
Purchase #4	$247.64	13.696%	$281.5568	$281.56	$281.55	$281.60
Purchase #5	$190.88	10.793%	$211.4817	$211.48	$211.50	$211.50
Purchase #6	$43.47	9.770%	$47.717	$47.72	$47.70	$47.70
Purchase #7	$110.39	8.332%	$119.5877	$119.59	$119.60	$119.60
7 purchase totals =	$963.49		$1,061.6053	$1,061.61	$1,061.65	$1,061.60