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 $211.29   6.744%   $225.5394   $225.54   $225.55   $225.50  
  Purchase #2 $213.69   3.861%   $221.9406   $221.94   $221.95   $221.90  
  Purchase #3 $58.49   11.120%   $64.9941   $64.99   $65.00   $65.00  
  Purchase #4 $62.59   5.841%   $66.2459   $66.25   $66.25   $66.20  
  Purchase #5 $168.74   6.672%   $179.9983   $180.00   $180.00   $180.00  
  Purchase #6 $174.85   10.396%   $193.0274   $193.03   $193.05   $193.00  
  Purchase #7 $77.62   7.422%   $83.381   $83.38   $83.40   $83.40  
  7 purchase totals = $967.27       $1,035.1267   $1,035.13   $1,035.20   $1,035.00