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	$66.43	9.646%	$72.8378	$72.84	$72.85	$72.80
Purchase #2	$34.86	8.771%	$37.9176	$37.92	$37.90	$37.90
Purchase #3	$107.87	3.210%	$111.3326	$111.33	$111.35	$111.30
Purchase #4	$54.74	7.871%	$59.0486	$59.05	$59.05	$59.00
Purchase #5	$225.99	7.621%	$243.2127	$243.21	$243.20	$243.20
Purchase #6	$133.51	13.591%	$151.6553	$151.66	$151.65	$151.70
Purchase #7	$184.65	13.139%	$208.9112	$208.91	$208.90	$208.90
7 purchase totals =	$808.05		$884.9158	$884.92	$884.90	$884.80