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 $222.25   4.417%   $232.0668   $232.07   $232.05   $232.10  
  Purchase #2 $234.68   13.348%   $266.0051   $266.01   $266.00   $266.00  
  Purchase #3 $86.69   9.680%   $95.0816   $95.08   $95.10   $95.10  
  Purchase #4 $108.90   4.646%   $113.9595   $113.96   $113.95   $114.00  
  Purchase #5 $220.69   3.696%   $228.8467   $228.85   $228.85   $228.80  
  Purchase #6 $84.37   12.578%   $94.9821   $94.98   $95.00   $95.00  
  Purchase #7 $112.42   9.124%   $122.6772   $122.68   $122.70   $122.70  
  7 purchase totals = $1,070.00       $1,153.6190   $1,153.63   $1,153.65   $1,153.70