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	$231.81	3.793%	$240.6026	$240.60	$240.60	$240.60
Purchase #2	$237.49	11.794%	$265.4996	$265.50	$265.50	$265.50
Purchase #3	$76.45	13.551%	$86.8097	$86.81	$86.80	$86.80
Purchase #4	$31.54	9.726%	$34.6076	$34.61	$34.60	$34.60
Purchase #5	$243.58	10.368%	$268.8344	$268.83	$268.85	$268.80
Purchase #6	$104.55	4.580%	$109.3384	$109.34	$109.35	$109.30
Purchase #7	$214.43	3.642%	$222.2395	$222.24	$222.25	$222.20
7 purchase totals =	$1,139.85		$1,227.9318	$1,227.93	$1,227.95	$1,227.80