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 $182.61   8.391%   $197.9328   $197.93   $197.95   $197.90  
  Purchase #2 $195.34   7.823%   $210.6214   $210.62   $210.60   $210.60  
  Purchase #3 $33.95   9.171%   $37.0636   $37.06   $37.05   $37.10  
  Purchase #4 $12.71   10.145%   $13.9994   $14.00   $14.00   $14.00  
  Purchase #5 $52.55   6.566%   $56.0004   $56.00   $56.00   $56.00  
  Purchase #6 $194.78   8.679%   $211.685   $211.69   $211.70   $211.70  
  Purchase #7 $183.61   8.312%   $198.8717   $198.87   $198.85   $198.90  
  7 purchase totals = $855.55       $926.1743   $926.17   $926.15   $926.20