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	$225.87	5.540%	$238.3832	$238.38	$238.40	$238.40
Purchase #2	$84.34	6.520%	$89.839	$89.84	$89.85	$89.80
Purchase #3	$180.35	11.606%	$201.2814	$201.28	$201.30	$201.30
Purchase #4	$20.36	3.339%	$21.0398	$21.04	$21.05	$21.00
Purchase #5	$164.50	6.787%	$175.6646	$175.66	$175.65	$175.70
Purchase #6	$136.40	5.193%	$143.4833	$143.48	$143.50	$143.50
Purchase #7	$128.72	3.201%	$132.8403	$132.84	$132.85	$132.80
7 purchase totals =	$940.54		$1,002.5316	$1,002.52	$1,002.60	$1,002.50