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 $86.34   12.619%   $97.2352   $97.24   $97.25   $97.20  
  Purchase #2 $167.55   6.122%   $177.8074   $177.81   $177.80   $177.80  
  Purchase #3 $121.69   13.241%   $137.803   $137.80   $137.80   $137.80  
  Purchase #4 $245.55   3.533%   $254.2253   $254.23   $254.25   $254.20  
  Purchase #5 $193.26   13.197%   $218.7645   $218.76   $218.75   $218.80  
  Purchase #6 $53.32   10.143%   $58.7282   $58.73   $58.75   $58.70  
  Purchase #7 $85.34   12.433%   $95.9503   $95.95   $95.95   $96.00  
  7 purchase totals = $953.05       $1,040.5139   $1,040.52   $1,040.55   $1,040.50