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 $87.54   8.531%   $95.008   $95.01   $95.00   $95.00  
  Purchase #2 $165.87   8.450%   $179.886   $179.89   $179.90   $179.90  
  Purchase #3 $197.81   12.407%   $222.3523   $222.35   $222.35   $222.40  
  Purchase #4 $211.88   8.182%   $229.216   $229.22   $229.20   $229.20  
  Purchase #5 $69.30   7.452%   $74.4642   $74.46   $74.45   $74.50  
  Purchase #6 $37.59   3.671%   $38.9699   $38.97   $38.95   $39.00  
  Purchase #7 $59.95   6.612%   $63.9139   $63.91   $63.90   $63.90  
  7 purchase totals = $829.94       $903.8103   $903.81   $903.75   $903.90