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	$43.59	3.336%	$45.0442	$45.04	$45.05	$45.00
Purchase #2	$159.52	4.677%	$166.9808	$166.98	$167.00	$167.00
Purchase #3	$128.52	7.149%	$137.7079	$137.71	$137.70	$137.70
Purchase #4	$81.51	10.636%	$90.1794	$90.18	$90.20	$90.20
Purchase #5	$59.37	3.140%	$61.2342	$61.23	$61.25	$61.20
Purchase #6	$227.50	6.376%	$242.0054	$242.01	$242.00	$242.00
Purchase #7	$58.62	8.585%	$63.6525	$63.65	$63.65	$63.70
7 purchase totals =	$758.63		$806.8044	$806.80	$806.85	$806.80