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 $148.29   10.395%   $163.7047   $163.70   $163.70   $163.70  
  Purchase #2 $233.72   13.208%   $264.5897   $264.59   $264.60   $264.60  
  Purchase #3 $114.93   12.789%   $129.6284   $129.63   $129.65   $129.60  
  Purchase #4 $144.37   4.265%   $150.5274   $150.53   $150.55   $150.50  
  Purchase #5 $178.66   6.551%   $190.364   $190.36   $190.35   $190.40  
  Purchase #6 $117.63   11.800%   $131.5103   $131.51   $131.50   $131.50  
  Purchase #7 $67.52   10.645%   $74.7075   $74.71   $74.70   $74.70  
  7 purchase totals = $1,005.12       $1,105.0320   $1,105.03   $1,105.05   $1,105.00