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 $62.99   10.835%   $69.815   $69.82   $69.80   $69.80  
  Purchase #2 $211.51   11.314%   $235.4402   $235.44   $235.45   $235.40  
  Purchase #3 $6.64   5.814%   $7.026   $7.03   $7.05   $7.00  
  Purchase #4 $217.98   12.310%   $244.8133   $244.81   $244.80   $244.80  
  Purchase #5 $150.91   9.669%   $165.5015   $165.50   $165.50   $165.50  
  Purchase #6 $216.49   13.498%   $245.7118   $245.71   $245.70   $245.70  
  Purchase #7 $234.90   10.333%   $259.1722   $259.17   $259.15   $259.20  
  7 purchase totals = $1,101.42       $1,227.4800   $1,227.48   $1,227.45   $1,227.40