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	$239.63	11.107%	$266.2457	$266.25	$266.25	$266.20
Purchase #2	$43.54	13.274%	$49.3195	$49.32	$49.30	$49.30
Purchase #3	$54.60	5.470%	$57.5866	$57.59	$57.60	$57.60
Purchase #4	$196.64	6.737%	$209.8876	$209.89	$209.90	$209.90
Purchase #5	$40.57	3.700%	$42.0711	$42.07	$42.05	$42.10
Purchase #6	$47.79	4.605%	$49.9907	$49.99	$50.00	$50.00
Purchase #7	$118.69	11.667%	$132.5376	$132.54	$132.55	$132.50
7 purchase totals =	$741.46		$807.6388	$807.65	$807.65	$807.60