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 $246.76   7.478%   $265.2127   $265.21   $265.20   $265.20  
  Purchase #2 $94.83   7.861%   $102.2846   $102.28   $102.30   $102.30  
  Purchase #3 $32.33   6.207%   $34.3367   $34.34   $34.35   $34.30  
  Purchase #4 $53.94   5.141%   $56.7131   $56.71   $56.70   $56.70  
  Purchase #5 $62.90   9.857%   $69.1001   $69.10   $69.10   $69.10  
  Purchase #6 $150.69   13.809%   $171.4988   $171.50   $171.50   $171.50  
  Purchase #7 $53.77   8.811%   $58.5077   $58.51   $58.50   $58.50  
  7 purchase totals = $695.22       $757.6537   $757.65   $757.65   $757.60