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 $84.36   10.194%   $92.9597   $92.96   $92.95   $93.00  
  Purchase #2 $183.69   4.730%   $192.3785   $192.38   $192.40   $192.40  
  Purchase #3 $135.43   5.366%   $142.6972   $142.70   $142.70   $142.70  
  Purchase #4 $122.96   3.477%   $127.2353   $127.24   $127.25   $127.20  
  Purchase #5 $45.84   4.339%   $47.829   $47.83   $47.85   $47.80  
  Purchase #6 $168.52   7.863%   $181.7707   $181.77   $181.75   $181.80  
  Purchase #7 $200.81   7.671%   $216.2141   $216.21   $216.20   $216.20  
  7 purchase totals = $941.61       $1,001.0845   $1,001.09   $1,001.10   $1,001.10