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	$215.60	10.588%	$238.4277	$238.43	$238.45	$238.40
Purchase #2	$7.83	4.869%	$8.2112	$8.21	$8.20	$8.20
Purchase #3	$123.42	12.569%	$138.9327	$138.93	$138.95	$138.90
Purchase #4	$42.81	8.544%	$46.4677	$46.47	$46.45	$46.50
Purchase #5	$215.90	10.290%	$238.1161	$238.12	$238.10	$238.10
Purchase #6	$119.91	9.756%	$131.6084	$131.61	$131.60	$131.60
Purchase #7	$105.97	10.253%	$116.8351	$116.84	$116.85	$116.80
7 purchase totals =	$831.44		$918.5989	$918.61	$918.60	$918.50