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 $213.54   10.370%   $235.6841   $235.68   $235.70   $235.70  
  Purchase #2 $22.64   6.285%   $24.0629   $24.06   $24.05   $24.10  
  Purchase #3 $110.92   4.715%   $116.1499   $116.15   $116.15   $116.10  
  Purchase #4 $67.68   11.704%   $75.6013   $75.60   $75.60   $75.60  
  Purchase #5 $172.89   6.725%   $184.5169   $184.52   $184.50   $184.50  
  Purchase #6 $213.31   5.318%   $224.6538   $224.65   $224.65   $224.70  
  Purchase #7 $25.30   5.247%   $26.6275   $26.63   $26.65   $26.60  
  7 purchase totals = $826.28       $887.2964   $887.29   $887.30   $887.30