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 $113.85   7.692%   $122.6073   $122.61   $122.60   $122.60  
  Purchase #2 $229.83   8.782%   $250.0137   $250.01   $250.00   $250.00  
  Purchase #3 $57.83   10.722%   $64.0305   $64.03   $64.05   $64.00  
  Purchase #4 $52.67   6.392%   $56.0367   $56.04   $56.05   $56.00  
  Purchase #5 $26.48   6.415%   $28.1787   $28.18   $28.20   $28.20  
  Purchase #6 $100.67   10.492%   $111.2323   $111.23   $111.25   $111.20  
  Purchase #7 $70.45   5.340%   $74.212   $74.21   $74.20   $74.20  
  7 purchase totals = $651.78       $706.3112   $706.31   $706.35   $706.20