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 $59.52   4.831%   $62.3954   $62.40   $62.40   $62.40  
  Purchase #2 $72.65   3.770%   $75.3889   $75.39   $75.40   $75.40  
  Purchase #3 $152.44   8.442%   $165.309   $165.31   $165.30   $165.30  
  Purchase #4 $223.39   4.265%   $232.9176   $232.92   $232.90   $232.90  
  Purchase #5 $180.61   11.605%   $201.5698   $201.57   $201.55   $201.60  
  Purchase #6 $53.70   5.259%   $56.5241   $56.52   $56.50   $56.50  
  Purchase #7 $16.73   3.184%   $17.2627   $17.26   $17.25   $17.30  
  7 purchase totals = $759.04       $811.3675   $811.37   $811.30   $811.40