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 $60.73   4.711%   $63.591   $63.59   $63.60   $63.60  
  Purchase #2 $214.46   12.642%   $241.572   $241.57   $241.55   $241.60  
  Purchase #3 $204.26   12.774%   $230.3522   $230.35   $230.35   $230.40  
  Purchase #4 $237.85   5.705%   $251.4193   $251.42   $251.40   $251.40  
  Purchase #5 $110.70   13.158%   $125.2659   $125.27   $125.25   $125.30  
  Purchase #6 $229.38   9.874%   $252.029   $252.03   $252.05   $252.00  
  Purchase #7 $35.65   13.331%   $40.4025   $40.40   $40.40   $40.40  
  7 purchase totals = $1,093.03       $1,204.6319   $1,204.63   $1,204.60   $1,204.70