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 $116.67   7.176%   $125.0422   $125.04   $125.05   $125.00  
  Purchase #2 $110.52   5.488%   $116.5853   $116.59   $116.60   $116.60  
  Purchase #3 $79.75   10.852%   $88.4045   $88.40   $88.40   $88.40  
  Purchase #4 $245.73   6.259%   $261.1102   $261.11   $261.10   $261.10  
  Purchase #5 $80.86   9.439%   $88.4924   $88.49   $88.50   $88.50  
  Purchase #6 $222.49   7.691%   $239.6017   $239.60   $239.60   $239.60  
  Purchase #7 $53.61   5.866%   $56.7548   $56.75   $56.75   $56.80  
  7 purchase totals = $909.63       $975.9911   $975.98   $976.00   $976.00