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 $62.27   11.706%   $69.5593   $69.56   $69.55   $69.60  
  Purchase #2 $154.89   4.281%   $161.5208   $161.52   $161.50   $161.50  
  Purchase #3 $63.69   13.347%   $72.1907   $72.19   $72.20   $72.20  
  Purchase #4 $193.74   10.313%   $213.7204   $213.72   $213.70   $213.70  
  Purchase #5 $144.40   9.479%   $158.0877   $158.09   $158.10   $158.10  
  Purchase #6 $233.49   5.713%   $246.8293   $246.83   $246.85   $246.80  
  Purchase #7 $174.91   4.560%   $182.8859   $182.89   $182.90   $182.90  
  7 purchase totals = $1,027.39       $1,104.7941   $1,104.80   $1,104.80   $1,104.80