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 $209.34   13.135%   $236.8368   $236.84   $236.85   $236.80  
  Purchase #2 $41.95   4.284%   $43.7471   $43.75   $43.75   $43.70  
  Purchase #3 $152.58   12.824%   $172.1469   $172.15   $172.15   $172.10  
  Purchase #4 $83.41   12.516%   $93.8496   $93.85   $93.85   $93.80  
  Purchase #5 $187.59   10.373%   $207.0487   $207.05   $207.05   $207.00  
  Purchase #6 $190.38   5.382%   $200.6263   $200.63   $200.65   $200.60  
  Purchase #7 $53.42   13.220%   $60.4821   $60.48   $60.50   $60.50  
  7 purchase totals = $918.67       $1,014.7375   $1,014.75   $1,014.80   $1,014.50