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 $41.79   3.351%   $43.1904   $43.19   $43.20   $43.20  
  Purchase #2 $181.96   8.596%   $197.6013   $197.60   $197.60   $197.60  
  Purchase #3 $217.63   12.779%   $245.4409   $245.44   $245.45   $245.40  
  Purchase #4 $139.74   11.548%   $155.8772   $155.88   $155.90   $155.90  
  Purchase #5 $200.64   3.320%   $207.3012   $207.30   $207.30   $207.30  
  Purchase #6 $218.93   6.205%   $232.5146   $232.51   $232.50   $232.50  
  Purchase #7 $201.78   7.391%   $216.6936   $216.69   $216.70   $216.70  
  7 purchase totals = $1,202.47       $1,298.6192   $1,298.61   $1,298.65   $1,298.60