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 $88.74   9.261%   $96.9582   $96.96   $96.95   $97.00  
  Purchase #2 $219.26   6.615%   $233.764   $233.76   $233.75   $233.80  
  Purchase #3 $8.63   13.714%   $9.8135   $9.81   $9.80   $9.80  
  Purchase #4 $165.68   5.619%   $174.9896   $174.99   $175.00   $175.00  
  Purchase #5 $207.25   4.524%   $216.626   $216.63   $216.65   $216.60  
  Purchase #6 $116.76   11.856%   $130.6031   $130.60   $130.60   $130.60  
  Purchase #7 $73.66   11.219%   $81.9239   $81.92   $81.90   $81.90  
  7 purchase totals = $879.98       $944.6783   $944.67   $944.65   $944.70