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 $84.77   13.132%   $95.902   $95.90   $95.90   $95.90  
  Purchase #2 $57.35   12.861%   $64.7258   $64.73   $64.75   $64.70  
  Purchase #3 $222.71   9.508%   $243.8853   $243.89   $243.90   $243.90  
  Purchase #4 $25.89   13.560%   $29.4007   $29.40   $29.40   $29.40  
  Purchase #5 $196.99   12.681%   $221.9703   $221.97   $221.95   $222.00  
  Purchase #6 $102.37   9.705%   $112.305   $112.31   $112.30   $112.30  
  Purchase #7 $97.86   10.215%   $107.8564   $107.86   $107.85   $107.90  
  7 purchase totals = $787.94       $876.0455   $876.06   $876.05   $876.10