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 $32.79   9.301%   $35.8398   $35.84   $35.85   $35.80  
  Purchase #2 $218.38   13.407%   $247.6582   $247.66   $247.65   $247.70  
  Purchase #3 $102.36   6.609%   $109.125   $109.13   $109.15   $109.10  
  Purchase #4 $174.95   12.621%   $197.0304   $197.03   $197.05   $197.00  
  Purchase #5 $107.75   6.656%   $114.9218   $114.92   $114.90   $114.90  
  Purchase #6 $117.61   5.739%   $124.3596   $124.36   $124.35   $124.40  
  Purchase #7 $213.64   8.488%   $231.7738   $231.77   $231.75   $231.80  
  7 purchase totals = $967.48       $1,060.7086   $1,060.71   $1,060.70   $1,060.70