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 $114.79   3.709%   $119.0476   $119.05   $119.05   $119.00  
  Purchase #2 $228.32   8.452%   $247.6176   $247.62   $247.60   $247.60  
  Purchase #3 $209.77   3.288%   $216.6672   $216.67   $216.65   $216.70  
  Purchase #4 $91.70   13.347%   $103.9392   $103.94   $103.95   $103.90  
  Purchase #5 $212.92   6.526%   $226.8152   $226.82   $226.80   $226.80  
  Purchase #6 $168.71   7.860%   $181.9706   $181.97   $181.95   $182.00  
  Purchase #7 $243.86   6.787%   $260.4108   $260.41   $260.40   $260.40  
  7 purchase totals = $1,270.07       $1,356.4682   $1,356.48   $1,356.40   $1,356.40