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 $82.33   13.809%   $93.6989   $93.70   $93.70   $93.70  
  Purchase #2 $88.57   4.611%   $92.654   $92.65   $92.65   $92.70  
  Purchase #3 $100.98   8.210%   $109.2705   $109.27   $109.25   $109.30  
  Purchase #4 $234.53   4.387%   $244.8188   $244.82   $244.80   $244.80  
  Purchase #5 $91.31   8.124%   $98.728   $98.73   $98.75   $98.70  
  Purchase #6 $56.61   4.255%   $59.0188   $59.02   $59.00   $59.00  
  Purchase #7 $191.29   4.463%   $199.8273   $199.83   $199.85   $199.80  
  7 purchase totals = $845.62       $898.0163   $898.02   $898.00   $898.00