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 $174.95   12.770%   $197.2911   $197.29   $197.30   $197.30  
  Purchase #2 $197.67   6.185%   $209.8959   $209.90   $209.90   $209.90  
  Purchase #3 $34.33   5.334%   $36.1612   $36.16   $36.15   $36.20  
  Purchase #4 $226.29   12.657%   $254.9315   $254.93   $254.95   $254.90  
  Purchase #5 $151.87   8.432%   $164.6757   $164.68   $164.70   $164.70  
  Purchase #6 $19.89   6.808%   $21.2441   $21.24   $21.25   $21.20  
  Purchase #7 $155.87   5.852%   $164.9915   $164.99   $165.00   $165.00  
  7 purchase totals = $960.87       $1,049.1910   $1,049.19   $1,049.25   $1,049.20