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 $68.66   4.473%   $71.7312   $71.73   $71.75   $71.70  
  Purchase #2 $186.71   6.759%   $199.3297   $199.33   $199.35   $199.30  
  Purchase #3 $151.58   13.385%   $171.869   $171.87   $171.85   $171.90  
  Purchase #4 $75.32   13.673%   $85.6185   $85.62   $85.60   $85.60  
  Purchase #5 $232.69   6.358%   $247.4844   $247.48   $247.50   $247.50  
  Purchase #6 $200.55   3.419%   $207.4068   $207.41   $207.40   $207.40  
  Purchase #7 $108.76   9.319%   $118.8953   $118.90   $118.90   $118.90  
  7 purchase totals = $1,024.27       $1,102.3349   $1,102.34   $1,102.35   $1,102.30