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 $126.46   13.814%   $143.9292   $143.93   $143.95   $143.90  
  Purchase #2 $237.79   5.444%   $250.7353   $250.74   $250.75   $250.70  
  Purchase #3 $25.78   5.444%   $27.1835   $27.18   $27.20   $27.20  
  Purchase #4 $149.61   7.458%   $160.7679   $160.77   $160.75   $160.80  
  Purchase #5 $137.99   11.299%   $153.5815   $153.58   $153.60   $153.60  
  Purchase #6 $179.66   11.319%   $199.9957   $200.00   $200.00   $200.00  
  Purchase #7 $83.38   3.574%   $86.36   $86.36   $86.35   $86.40  
  7 purchase totals = $940.67       $1,022.5531   $1,022.56   $1,022.60   $1,022.60