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	$107.78	7.521%	$115.8861	$115.89	$115.90	$115.90
Purchase #2	$80.45	11.210%	$89.4684	$89.47	$89.45	$89.50
Purchase #3	$91.92	9.612%	$100.7554	$100.76	$100.75	$100.80
Purchase #4	$149.34	13.514%	$169.5218	$169.52	$169.50	$169.50
Purchase #5	$30.90	13.692%	$35.1308	$35.13	$35.15	$35.10
Purchase #6	$145.29	11.252%	$161.638	$161.64	$161.65	$161.60
Purchase #7	$221.25	11.189%	$246.0057	$246.01	$246.00	$246.00
7 purchase totals =	$826.93		$918.4062	$918.42	$918.40	$918.40