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 $163.93   6.529%   $174.633   $174.63   $174.65   $174.60  
  Purchase #2 $176.54   13.442%   $200.2705   $200.27   $200.25   $200.30  
  Purchase #3 $192.60   3.418%   $199.1831   $199.18   $199.20   $199.20  
  Purchase #4 $102.55   13.628%   $116.5255   $116.53   $116.55   $116.50  
  Purchase #5 $183.68   8.609%   $199.493   $199.49   $199.50   $199.50  
  Purchase #6 $32.44   3.328%   $33.5196   $33.52   $33.50   $33.50  
  Purchase #7 $74.78   5.678%   $79.026   $79.03   $79.05   $79.00  
  7 purchase totals = $926.52       $1,002.6507   $1,002.65   $1,002.70   $1,002.60