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 $59.48   4.274%   $62.0222   $62.02   $62.00   $62.00  
  Purchase #2 $87.65   8.564%   $95.1563   $95.16   $95.15   $95.20  
  Purchase #3 $10.48   9.872%   $11.5146   $11.51   $11.50   $11.50  
  Purchase #4 $177.64   7.823%   $191.5368   $191.54   $191.55   $191.50  
  Purchase #5 $92.30   10.622%   $102.1041   $102.10   $102.10   $102.10  
  Purchase #6 $82.93   8.165%   $89.7012   $89.70   $89.70   $89.70  
  Purchase #7 $180.26   7.212%   $193.2604   $193.26   $193.25   $193.30  
  7 purchase totals = $690.74       $745.2956   $745.29   $745.25   $745.30