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	$74.92	4.401%	$78.2172	$78.22	$78.20	$78.20
Purchase #2	$124.45	3.595%	$128.924	$128.92	$128.90	$128.90
Purchase #3	$236.39	10.615%	$261.4828	$261.48	$261.50	$261.50
Purchase #4	$9.78	10.358%	$10.793	$10.79	$10.80	$10.80
Purchase #5	$83.61	9.407%	$91.4752	$91.48	$91.50	$91.50
Purchase #6	$52.51	8.426%	$56.9345	$56.93	$56.95	$56.90
Purchase #7	$231.59	3.484%	$239.6586	$239.66	$239.65	$239.70
7 purchase totals =	$813.25		$867.4853	$867.48	$867.50	$867.50