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 $176.93   13.665%   $201.1075   $201.11   $201.10   $201.10  
  Purchase #2 $225.65   9.740%   $247.6283   $247.63   $247.65   $247.60  
  Purchase #3 $53.94   11.477%   $60.1307   $60.13   $60.15   $60.10  
  Purchase #4 $242.40   3.499%   $250.8816   $250.88   $250.90   $250.90  
  Purchase #5 $133.85   5.557%   $141.288   $141.29   $141.30   $141.30  
  Purchase #6 $101.35   5.484%   $106.908   $106.91   $106.90   $106.90  
  Purchase #7 $133.34   9.615%   $146.1606   $146.16   $146.15   $146.20  
  7 purchase totals = $1,067.46       $1,154.1047   $1,154.11   $1,154.15   $1,154.10