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	$224.29	5.830%	$237.3661	$237.37	$237.35	$237.40
Purchase #2	$63.79	7.347%	$68.4767	$68.48	$68.50	$68.50
Purchase #3	$90.61	11.373%	$100.9151	$100.92	$100.90	$100.90
Purchase #4	$242.86	11.182%	$270.0166	$270.02	$270.00	$270.00
Purchase #5	$86.47	3.363%	$89.378	$89.38	$89.40	$89.40
Purchase #6	$166.62	10.476%	$184.0751	$184.08	$184.10	$184.10
Purchase #7	$210.71	8.576%	$228.7805	$228.78	$228.80	$228.80
7 purchase totals =	$1,085.35		$1,179.0081	$1,179.03	$1,179.05	$1,179.10