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 $246.85   7.350%   $264.9935   $264.99   $265.00   $265.00  
  Purchase #2 $67.51   12.628%   $76.0352   $76.04   $76.05   $76.00  
  Purchase #3 $84.37   3.484%   $87.3095   $87.31   $87.30   $87.30  
  Purchase #4 $234.53   10.266%   $258.6068   $258.61   $258.60   $258.60  
  Purchase #5 $186.87   13.857%   $212.7646   $212.76   $212.75   $212.80  
  Purchase #6 $12.26   4.447%   $12.8052   $12.81   $12.80   $12.80  
  Purchase #7 $174.52   9.842%   $191.6963   $191.70   $191.70   $191.70  
  7 purchase totals = $1,006.91       $1,104.2111   $1,104.22   $1,104.20   $1,104.20