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 $93.60   13.169%   $105.9262   $105.93   $105.95   $105.90  
  Purchase #2 $239.94   9.870%   $263.6221   $263.62   $263.60   $263.60  
  Purchase #3 $6.74   13.200%   $7.6297   $7.63   $7.65   $7.60  
  Purchase #4 $177.40   8.564%   $192.5925   $192.59   $192.60   $192.60  
  Purchase #5 $119.92   10.223%   $132.1794   $132.18   $132.20   $132.20  
  Purchase #6 $7.59   7.760%   $8.179   $8.18   $8.20   $8.20  
  Purchase #7 $60.86   8.294%   $65.9077   $65.91   $65.90   $65.90  
  7 purchase totals = $706.05       $776.0366   $776.04   $776.10   $776.00