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 $56.79   9.867%   $62.3935   $62.39   $62.40   $62.40  
  Purchase #2 $86.95   9.550%   $95.2537   $95.25   $95.25   $95.30  
  Purchase #3 $86.73   12.814%   $97.8436   $97.84   $97.85   $97.80  
  Purchase #4 $193.53   6.462%   $206.0359   $206.04   $206.05   $206.00  
  Purchase #5 $224.57   4.427%   $234.5117   $234.51   $234.50   $234.50  
  Purchase #6 $169.33   12.357%   $190.2541   $190.25   $190.25   $190.30  
  Purchase #7 $24.64   3.183%   $25.4243   $25.42   $25.40   $25.40  
  7 purchase totals = $842.54       $911.7168   $911.70   $911.70   $911.70