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 $119.25   5.369%   $125.6525   $125.65   $125.65   $125.70  
  Purchase #2 $8.47   13.412%   $9.606   $9.61   $9.60   $9.60  
  Purchase #3 $32.70   6.650%   $34.8746   $34.87   $34.85   $34.90  
  Purchase #4 $234.72   12.414%   $263.8581   $263.86   $263.85   $263.90  
  Purchase #5 $198.44   11.574%   $221.4074   $221.41   $221.40   $221.40  
  Purchase #6 $250.73   6.706%   $267.544   $267.54   $267.55   $267.50  
  Purchase #7 $120.38   11.776%   $134.5559   $134.56   $134.55   $134.60  
  7 purchase totals = $964.69       $1,057.4985   $1,057.50   $1,057.45   $1,057.60