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	$189.39	5.306%	$199.439	$199.44	$199.45	$199.40
Purchase #2	$136.59	10.518%	$150.9565	$150.96	$150.95	$151.00
Purchase #3	$187.33	13.656%	$212.9118	$212.91	$212.90	$212.90
Purchase #4	$157.86	3.156%	$162.8421	$162.84	$162.85	$162.80
Purchase #5	$31.90	6.162%	$33.8657	$33.87	$33.85	$33.90
Purchase #6	$102.59	13.189%	$116.1206	$116.12	$116.10	$116.10
Purchase #7	$71.54	6.725%	$76.3511	$76.35	$76.35	$76.40
7 purchase totals =	$877.20		$952.4868	$952.49	$952.45	$952.50