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 $62.63   9.621%   $68.6556   $68.66   $68.65   $68.70  
  Purchase #2 $241.53   3.709%   $250.4883   $250.49   $250.50   $250.50  
  Purchase #3 $230.97   5.183%   $242.9412   $242.94   $242.95   $242.90  
  Purchase #4 $128.56   10.832%   $142.4856   $142.49   $142.50   $142.50  
  Purchase #5 $79.36   10.807%   $87.9364   $87.94   $87.95   $87.90  
  Purchase #6 $219.90   10.684%   $243.3941   $243.39   $243.40   $243.40  
  Purchase #7 $166.46   7.328%   $178.6582   $178.66   $178.65   $178.70  
  7 purchase totals = $1,129.41       $1,214.5594   $1,214.57   $1,214.60   $1,214.60