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	$215.67	10.641%	$238.6194	$238.62	$238.60	$238.60
Purchase #2	$194.69	5.198%	$204.81	$204.81	$204.80	$204.80
Purchase #3	$195.45	8.831%	$212.7102	$212.71	$212.70	$212.70
Purchase #4	$20.79	3.660%	$21.5509	$21.55	$21.55	$21.60
Purchase #5	$35.81	5.650%	$37.8333	$37.83	$37.85	$37.80
Purchase #6	$77.61	3.736%	$80.5095	$80.51	$80.50	$80.50
Purchase #7	$92.86	9.183%	$101.3873	$101.39	$101.40	$101.40
7 purchase totals =	$832.88		$897.4206	$897.42	$897.40	$897.40