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	$32.93	7.205%	$35.3026	$35.30	$35.30	$35.30
Purchase #2	$123.43	13.831%	$140.5016	$140.50	$140.50	$140.50
Purchase #3	$16.64	5.721%	$17.592	$17.59	$17.60	$17.60
Purchase #4	$42.78	6.270%	$45.4623	$45.46	$45.45	$45.50
Purchase #5	$77.43	5.639%	$81.7963	$81.80	$81.80	$81.80
Purchase #6	$56.81	8.333%	$61.544	$61.54	$61.55	$61.50
Purchase #7	$85.66	4.402%	$89.4308	$89.43	$89.45	$89.40
7 purchase totals =	$435.68		$471.6296	$471.62	$471.65	$471.60