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	$223.28	7.745%	$240.573	$240.57	$240.55	$240.60
Purchase #2	$9.92	6.354%	$10.5503	$10.55	$10.55	$10.60
Purchase #3	$67.90	5.633%	$71.7248	$71.72	$71.70	$71.70
Purchase #4	$117.45	12.434%	$132.0537	$132.05	$132.05	$132.10
Purchase #5	$20.71	7.220%	$22.2053	$22.21	$22.20	$22.20
Purchase #6	$13.56	13.751%	$15.4246	$15.42	$15.40	$15.40
Purchase #7	$160.39	7.616%	$172.6053	$172.61	$172.60	$172.60
7 purchase totals =	$613.21		$665.1370	$665.13	$665.05	$665.20