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	$191.87	13.323%	$217.4328	$217.43	$217.45	$217.40
Purchase #2	$96.60	6.768%	$103.1379	$103.14	$103.15	$103.10
Purchase #3	$192.99	13.315%	$218.6866	$218.69	$218.70	$218.70
Purchase #4	$141.70	6.162%	$150.4316	$150.43	$150.45	$150.40
Purchase #5	$96.96	9.636%	$106.3031	$106.30	$106.30	$106.30
Purchase #6	$168.61	12.626%	$189.8987	$189.90	$189.90	$189.90
Purchase #7	$91.81	3.841%	$95.3364	$95.34	$95.35	$95.30
7 purchase totals =	$980.54		$1,081.2271	$1,081.23	$1,081.30	$1,081.10