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 $97.68   7.598%   $105.1017   $105.10   $105.10   $105.10  
  Purchase #2 $246.67   8.299%   $267.1411   $267.14   $267.15   $267.10  
  Purchase #3 $228.73   7.189%   $245.1734   $245.17   $245.15   $245.20  
  Purchase #4 $58.32   5.752%   $61.6746   $61.67   $61.65   $61.70  
  Purchase #5 $204.74   10.492%   $226.2213   $226.22   $226.20   $226.20  
  Purchase #6 $140.49   12.186%   $157.6101   $157.61   $157.60   $157.60  
  Purchase #7 $149.43   9.295%   $163.3195   $163.32   $163.30   $163.30  
  7 purchase totals = $1,126.06       $1,226.2417   $1,226.23   $1,226.15   $1,226.20