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 $98.93   5.167%   $104.0417   $104.04   $104.05   $104.00  
  Purchase #2 $80.98   5.411%   $85.3618   $85.36   $85.35   $85.40  
  Purchase #3 $167.83   3.676%   $173.9994   $174.00   $174.00   $174.00  
  Purchase #4 $60.80   3.102%   $62.686   $62.69   $62.70   $62.70  
  Purchase #5 $171.80   4.426%   $179.4039   $179.40   $179.40   $179.40  
  Purchase #6 $121.96   11.859%   $136.4232   $136.42   $136.40   $136.40  
  Purchase #7 $249.67   9.159%   $272.5373   $272.54   $272.55   $272.50  
  7 purchase totals = $951.97       $1,014.4533   $1,014.45   $1,014.45   $1,014.40