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 $81.52   13.490%   $92.517   $92.52   $92.50   $92.50  
  Purchase #2 $143.58   9.200%   $156.7894   $156.79   $156.80   $156.80  
  Purchase #3 $167.58   4.227%   $174.6636   $174.66   $174.65   $174.70  
  Purchase #4 $41.64   7.493%   $44.7601   $44.76   $44.75   $44.80  
  Purchase #5 $248.46   3.645%   $257.5164   $257.52   $257.50   $257.50  
  Purchase #6 $164.30   3.293%   $169.7104   $169.71   $169.70   $169.70  
  Purchase #7 $105.74   12.526%   $118.985   $118.99   $119.00   $119.00  
  7 purchase totals = $952.82       $1,014.9419   $1,014.95   $1,014.90   $1,015.00