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 $116.68   7.709%   $125.6749   $125.67   $125.65   $125.70  
  Purchase #2 $125.42   13.731%   $142.6414   $142.64   $142.65   $142.60  
  Purchase #3 $71.47   12.545%   $80.4359   $80.44   $80.45   $80.40  
  Purchase #4 $151.51   6.115%   $160.7748   $160.77   $160.75   $160.80  
  Purchase #5 $215.87   13.724%   $245.496   $245.50   $245.50   $245.50  
  Purchase #6 $132.64   6.802%   $141.6622   $141.66   $141.65   $141.70  
  Purchase #7 $174.28   5.865%   $184.5015   $184.50   $184.50   $184.50  
  7 purchase totals = $987.87       $1,081.1867   $1,081.18   $1,081.15   $1,081.20