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	$110.38	12.246%	$123.8971	$123.90	$123.90	$123.90
Purchase #2	$214.34	6.194%	$227.6162	$227.62	$227.60	$227.60
Purchase #3	$108.77	4.293%	$113.4395	$113.44	$113.45	$113.40
Purchase #4	$86.97	4.160%	$90.588	$90.59	$90.60	$90.60
Purchase #5	$187.47	6.642%	$199.9218	$199.92	$199.90	$199.90
Purchase #6	$119.38	4.206%	$124.4011	$124.40	$124.40	$124.40
Purchase #7	$39.99	8.114%	$43.2348	$43.23	$43.25	$43.20
7 purchase totals =	$867.30		$923.0985	$923.10	$923.10	$923.00