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	$40.70	5.497%	$42.9373	$42.94	$42.95	$42.90
Purchase #2	$11.57	11.756%	$12.9302	$12.93	$12.95	$12.90
Purchase #3	$46.91	3.502%	$48.5528	$48.55	$48.55	$48.60
Purchase #4	$116.93	11.649%	$130.5512	$130.55	$130.55	$130.60
Purchase #5	$152.91	10.207%	$168.5175	$168.52	$168.50	$168.50
Purchase #6	$165.81	11.593%	$185.0324	$185.03	$185.05	$185.00
Purchase #7	$248.91	13.527%	$282.5801	$282.58	$282.60	$282.60
7 purchase totals =	$783.74		$871.1015	$871.10	$871.15	$871.10