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 $95.55   9.466%   $104.5948   $104.59   $104.60   $104.60  
  Purchase #2 $244.39   13.345%   $277.0038   $277.00   $277.00   $277.00  
  Purchase #3 $182.65   11.633%   $203.8977   $203.90   $203.90   $203.90  
  Purchase #4 $190.70   6.537%   $203.1661   $203.17   $203.15   $203.20  
  Purchase #5 $140.98   9.376%   $154.1983   $154.20   $154.20   $154.20  
  Purchase #6 $136.85   3.284%   $141.3442   $141.34   $141.35   $141.30  
  Purchase #7 $71.46   5.810%   $75.6118   $75.61   $75.60   $75.60  
  7 purchase totals = $1,062.58       $1,159.8167   $1,159.81   $1,159.80   $1,159.80