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 $58.76   6.334%   $62.4819   $62.48   $62.50   $62.50  
  Purchase #2 $171.37   8.668%   $186.2244   $186.22   $186.20   $186.20  
  Purchase #3 $240.63   8.751%   $261.6875   $261.69   $261.70   $261.70  
  Purchase #4 $221.29   11.394%   $246.5038   $246.50   $246.50   $246.50  
  Purchase #5 $102.54   5.244%   $107.9172   $107.92   $107.90   $107.90  
  Purchase #6 $149.46   6.104%   $158.583   $158.58   $158.60   $158.60  
  Purchase #7 $121.60   5.411%   $128.1798   $128.18   $128.20   $128.20  
  7 purchase totals = $1,065.65       $1,151.5776   $1,151.57   $1,151.60   $1,151.60