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 $182.72   10.116%   $201.204   $201.20   $201.20   $201.20  
  Purchase #2 $237.74   8.391%   $257.6888   $257.69   $257.70   $257.70  
  Purchase #3 $94.59   4.569%   $98.9118   $98.91   $98.90   $98.90  
  Purchase #4 $83.62   4.263%   $87.1847   $87.18   $87.20   $87.20  
  Purchase #5 $214.83   11.291%   $239.0865   $239.09   $239.10   $239.10  
  Purchase #6 $77.86   3.199%   $80.3507   $80.35   $80.35   $80.40  
  Purchase #7 $143.46   11.267%   $159.6236   $159.62   $159.60   $159.60  
  7 purchase totals = $1,034.82       $1,124.0501   $1,124.04   $1,124.05   $1,124.10