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 $57.30   8.636%   $62.2484   $62.25   $62.25   $62.20  
  Purchase #2 $201.62   7.690%   $217.1246   $217.12   $217.10   $217.10  
  Purchase #3 $56.84   3.112%   $58.6089   $58.61   $58.60   $58.60  
  Purchase #4 $18.38   11.722%   $20.5345   $20.53   $20.55   $20.50  
  Purchase #5 $191.33   8.184%   $206.9884   $206.99   $207.00   $207.00  
  Purchase #6 $225.67   11.518%   $251.6627   $251.66   $251.65   $251.70  
  Purchase #7 $45.95   3.426%   $47.5242   $47.52   $47.50   $47.50  
  7 purchase totals = $797.09       $864.6917   $864.68   $864.65   $864.60