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 $24.94   4.504%   $26.0633   $26.06   $26.05   $26.10  
  Purchase #2 $151.89   12.824%   $171.3684   $171.37   $171.35   $171.40  
  Purchase #3 $39.35   10.425%   $43.4522   $43.45   $43.45   $43.50  
  Purchase #4 $90.53   7.600%   $97.4103   $97.41   $97.40   $97.40  
  Purchase #5 $196.76   6.315%   $209.1854   $209.19   $209.20   $209.20  
  Purchase #6 $141.43   8.190%   $153.0131   $153.01   $153.00   $153.00  
  Purchase #7 $77.86   9.326%   $85.1212   $85.12   $85.10   $85.10  
  7 purchase totals = $722.76       $785.6139   $785.61   $785.55   $785.70