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	$131.41	10.608%	$145.35	$145.35	$145.35	$145.40
Purchase #2	$29.47	11.343%	$32.8128	$32.81	$32.80	$32.80
Purchase #3	$152.42	4.601%	$159.4328	$159.43	$159.45	$159.40
Purchase #4	$161.75	8.129%	$174.8987	$174.90	$174.90	$174.90
Purchase #5	$141.48	13.559%	$160.6633	$160.66	$160.65	$160.70
Purchase #6	$84.60	5.216%	$89.0127	$89.01	$89.00	$89.00
Purchase #7	$86.45	5.855%	$91.5116	$91.51	$91.50	$91.50
7 purchase totals =	$787.58		$853.6819	$853.67	$853.65	$853.70