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 $226.67   5.324%   $238.7379   $238.74   $238.75   $238.70  
  Purchase #2 $91.98   4.476%   $96.097   $96.10   $96.10   $96.10  
  Purchase #3 $113.41   3.867%   $117.7956   $117.80   $117.80   $117.80  
  Purchase #4 $224.32   4.709%   $234.8832   $234.88   $234.90   $234.90  
  Purchase #5 $69.69   7.126%   $74.6561   $74.66   $74.65   $74.70  
  Purchase #6 $164.92   10.188%   $181.722   $181.72   $181.70   $181.70  
  Purchase #7 $173.78   9.687%   $190.6141   $190.61   $190.60   $190.60  
  7 purchase totals = $1,064.77       $1,134.5059   $1,134.51   $1,134.50   $1,134.50