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 $102.66   10.551%   $113.4917   $113.49   $113.50   $113.50  
  Purchase #2 $142.57   8.262%   $154.3491   $154.35   $154.35   $154.30  
  Purchase #3 $9.81   8.228%   $10.6172   $10.62   $10.60   $10.60  
  Purchase #4 $223.68   12.488%   $251.6132   $251.61   $251.60   $251.60  
  Purchase #5 $214.95   8.446%   $233.1047   $233.10   $233.10   $233.10  
  Purchase #6 $110.26   10.117%   $121.415   $121.42   $121.40   $121.40  
  Purchase #7 $219.84   10.232%   $242.334   $242.33   $242.35   $242.30  
  7 purchase totals = $1,023.77       $1,126.9249   $1,126.92   $1,126.90   $1,126.80