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 $60.48   5.602%   $63.8681   $63.87   $63.85   $63.90  
  Purchase #2 $216.78   5.870%   $229.505   $229.51   $229.50   $229.50  
  Purchase #3 $193.37   4.486%   $202.0446   $202.04   $202.05   $202.00  
  Purchase #4 $205.72   5.665%   $217.374   $217.37   $217.35   $217.40  
  Purchase #5 $197.99   12.527%   $222.7922   $222.79   $222.80   $222.80  
  Purchase #6 $46.91   13.494%   $53.24   $53.24   $53.25   $53.20  
  Purchase #7 $179.58   3.229%   $185.3786   $185.38   $185.40   $185.40  
  7 purchase totals = $1,100.83       $1,174.2025   $1,174.20   $1,174.20   $1,174.20