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 $204.69   4.396%   $213.6882   $213.69   $213.70   $213.70  
  Purchase #2 $191.64   8.142%   $207.2433   $207.24   $207.25   $207.20  
  Purchase #3 $108.69   13.724%   $123.6066   $123.61   $123.60   $123.60  
  Purchase #4 $184.54   7.117%   $197.6737   $197.67   $197.65   $197.70  
  Purchase #5 $151.94   12.191%   $170.463   $170.46   $170.45   $170.50  
  Purchase #6 $90.87   4.760%   $95.1954   $95.20   $95.20   $95.20  
  Purchase #7 $147.42   12.738%   $166.1984   $166.20   $166.20   $166.20  
  7 purchase totals = $1,079.79       $1,174.0686   $1,174.07   $1,174.05   $1,174.10