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 $237.31   4.348%   $247.6282   $247.63   $247.65   $247.60  
  Purchase #2 $156.26   5.751%   $165.2465   $165.25   $165.25   $165.20  
  Purchase #3 $227.92   11.803%   $254.8214   $254.82   $254.80   $254.80  
  Purchase #4 $170.28   9.627%   $186.6729   $186.67   $186.65   $186.70  
  Purchase #5 $189.46   4.225%   $197.4647   $197.46   $197.45   $197.50  
  Purchase #6 $53.62   8.270%   $58.0544   $58.05   $58.05   $58.10  
  Purchase #7 $198.64   8.766%   $216.0528   $216.05   $216.05   $216.10  
  7 purchase totals = $1,233.49       $1,325.9409   $1,325.93   $1,325.90   $1,326.00