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 $111.33   7.584%   $119.7733   $119.77   $119.75   $119.80  
  Purchase #2 $185.38   9.167%   $202.3738   $202.37   $202.35   $202.40  
  Purchase #3 $100.42   8.684%   $109.1405   $109.14   $109.15   $109.10  
  Purchase #4 $154.33   13.670%   $175.4269   $175.43   $175.45   $175.40  
  Purchase #5 $151.44   7.744%   $163.1675   $163.17   $163.15   $163.20  
  Purchase #6 $247.26   9.837%   $271.583   $271.58   $271.60   $271.60  
  Purchase #7 $126.95   9.850%   $139.4546   $139.45   $139.45   $139.50  
  7 purchase totals = $1,077.11       $1,180.9196   $1,180.91   $1,180.90   $1,181.00