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 $107.59   6.435%   $114.5134   $114.51   $114.50   $114.50  
  Purchase #2 $57.42   3.382%   $59.3619   $59.36   $59.35   $59.40  
  Purchase #3 $246.47   11.525%   $274.8757   $274.88   $274.90   $274.90  
  Purchase #4 $247.64   10.811%   $274.4124   $274.41   $274.40   $274.40  
  Purchase #5 $223.80   9.797%   $245.7257   $245.73   $245.75   $245.70  
  Purchase #6 $151.84   6.267%   $161.3558   $161.36   $161.35   $161.40  
  Purchase #7 $63.95   13.151%   $72.3601   $72.36   $72.35   $72.40  
  7 purchase totals = $1,098.71       $1,202.6050   $1,202.61   $1,202.60   $1,202.70