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	$208.25	9.766%	$228.5877	$228.59	$228.60	$228.60
Purchase #2	$87.64	13.514%	$99.4837	$99.48	$99.50	$99.50
Purchase #3	$95.91	8.613%	$104.1707	$104.17	$104.15	$104.20
Purchase #4	$227.37	6.627%	$242.4378	$242.44	$242.45	$242.40
Purchase #5	$241.90	13.505%	$274.5686	$274.57	$274.55	$274.60
Purchase #6	$100.62	5.603%	$106.2577	$106.26	$106.25	$106.30
Purchase #7	$79.41	8.651%	$86.2798	$86.28	$86.30	$86.30
7 purchase totals =	$1,041.10		$1,141.7860	$1,141.79	$1,141.80	$1,141.90