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 $54.69   6.140%   $58.048   $58.05   $58.05   $58.00  
  Purchase #2 $225.95   3.790%   $234.5135   $234.51   $234.50   $234.50  
  Purchase #3 $144.79   4.138%   $150.7814   $150.78   $150.80   $150.80  
  Purchase #4 $61.46   10.599%   $67.9741   $67.97   $67.95   $68.00  
  Purchase #5 $232.51   12.330%   $261.1785   $261.18   $261.20   $261.20  
  Purchase #6 $203.84   5.397%   $214.8412   $214.84   $214.85   $214.80  
  Purchase #7 $44.78   4.198%   $46.6599   $46.66   $46.65   $46.70  
  7 purchase totals = $968.02       $1,033.9966   $1,033.99   $1,034.00   $1,034.00