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 $201.54   11.702%   $225.1242   $225.12   $225.10   $225.10  
  Purchase #2 $194.51   3.347%   $201.0202   $201.02   $201.00   $201.00  
  Purchase #3 $41.63   13.863%   $47.4012   $47.40   $47.40   $47.40  
  Purchase #4 $135.41   9.701%   $148.5461   $148.55   $148.55   $148.50  
  Purchase #5 $132.81   7.455%   $142.711   $142.71   $142.70   $142.70  
  Purchase #6 $125.49   12.820%   $141.5778   $141.58   $141.60   $141.60  
  Purchase #7 $140.93   9.201%   $153.897   $153.90   $153.90   $153.90  
  7 purchase totals = $972.32       $1,060.2775   $1,060.28   $1,060.25   $1,060.20