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	$147.32	5.599%	$155.5684	$155.57	$155.55	$155.60
Purchase #2	$39.67	9.185%	$43.3137	$43.31	$43.30	$43.30
Purchase #3	$79.88	3.273%	$82.4945	$82.49	$82.50	$82.50
Purchase #4	$162.25	4.476%	$169.5123	$169.51	$169.50	$169.50
Purchase #5	$175.76	5.526%	$185.4725	$185.47	$185.45	$185.50
Purchase #6	$59.76	7.184%	$64.0532	$64.05	$64.05	$64.10
Purchase #7	$144.99	12.636%	$163.3109	$163.31	$163.30	$163.30
7 purchase totals =	$809.63		$863.7255	$863.71	$863.65	$863.80