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 $116.64   7.644%   $125.556   $125.56   $125.55   $125.60  
  Purchase #2 $204.73   5.867%   $216.7415   $216.74   $216.75   $216.70  
  Purchase #3 $222.83   12.597%   $250.8999   $250.90   $250.90   $250.90  
  Purchase #4 $118.52   5.591%   $125.1465   $125.15   $125.15   $125.10  
  Purchase #5 $102.39   3.382%   $105.8528   $105.85   $105.85   $105.90  
  Purchase #6 $211.62   11.751%   $236.4875   $236.49   $236.50   $236.50  
  Purchase #7 $176.77   13.515%   $200.6605   $200.66   $200.65   $200.70  
  7 purchase totals = $1,153.50       $1,261.3447   $1,261.35   $1,261.35   $1,261.40