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	$190.40	9.335%	$208.1738	$208.17	$208.15	$208.20
Purchase #2	$91.48	11.620%	$102.11	$102.11	$102.10	$102.10
Purchase #3	$81.56	12.302%	$91.5935	$91.59	$91.60	$91.60
Purchase #4	$217.32	10.622%	$240.4037	$240.40	$240.40	$240.40
Purchase #5	$75.42	8.430%	$81.7779	$81.78	$81.80	$81.80
Purchase #6	$179.71	3.249%	$185.5488	$185.55	$185.55	$185.50
Purchase #7	$100.97	4.433%	$105.446	$105.45	$105.45	$105.40
7 purchase totals =	$936.86		$1,015.0537	$1,015.05	$1,015.05	$1,015.00