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	$212.43	3.313%	$219.4678	$219.47	$219.45	$219.50
Purchase #2	$146.28	7.775%	$157.6533	$157.65	$157.65	$157.70
Purchase #3	$96.50	6.217%	$102.4994	$102.50	$102.50	$102.50
Purchase #4	$90.40	9.604%	$99.082	$99.08	$99.10	$99.10
Purchase #5	$95.61	7.302%	$102.5914	$102.59	$102.60	$102.60
Purchase #6	$213.77	11.673%	$238.7234	$238.72	$238.70	$238.70
Purchase #7	$100.39	10.357%	$110.7874	$110.79	$110.80	$110.80
7 purchase totals =	$955.38		$1,030.8047	$1,030.80	$1,030.80	$1,030.90