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 $208.55   7.390%   $223.9618   $223.96   $223.95   $224.00  
  Purchase #2 $175.31   13.859%   $199.6062   $199.61   $199.60   $199.60  
  Purchase #3 $40.52   6.276%   $43.063   $43.06   $43.05   $43.10  
  Purchase #4 $5.43   4.602%   $5.6799   $5.68   $5.70   $5.70  
  Purchase #5 $110.37   8.275%   $119.5031   $119.50   $119.50   $119.50  
  Purchase #6 $220.36   5.684%   $232.8853   $232.89   $232.90   $232.90  
  Purchase #7 $248.70   7.734%   $267.9345   $267.93   $267.95   $267.90  
  7 purchase totals = $1,009.24       $1,092.6338   $1,092.63   $1,092.65   $1,092.70