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 $172.77   13.467%   $196.0369   $196.04   $196.05   $196.00  
  Purchase #2 $106.77   6.395%   $113.5979   $113.60   $113.60   $113.60  
  Purchase #3 $95.66   11.843%   $106.989   $106.99   $107.00   $107.00  
  Purchase #4 $117.36   5.206%   $123.4698   $123.47   $123.45   $123.50  
  Purchase #5 $42.73   6.283%   $45.4147   $45.41   $45.40   $45.40  
  Purchase #6 $170.47   7.731%   $183.649   $183.65   $183.65   $183.60  
  Purchase #7 $156.81   11.417%   $174.713   $174.71   $174.70   $174.70  
  7 purchase totals = $862.57       $943.8703   $943.87   $943.85   $943.80