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 $182.87   10.124%   $201.3838   $201.38   $201.40   $201.40  
  Purchase #2 $119.53   12.532%   $134.5095   $134.51   $134.50   $134.50  
  Purchase #3 $28.98   9.294%   $31.6734   $31.67   $31.65   $31.70  
  Purchase #4 $26.44   3.477%   $27.3593   $27.36   $27.35   $27.40  
  Purchase #5 $113.35   9.652%   $124.2905   $124.29   $124.30   $124.30  
  Purchase #6 $143.91   9.511%   $157.5973   $157.60   $157.60   $157.60  
  Purchase #7 $197.91   3.639%   $205.1119   $205.11   $205.10   $205.10  
  7 purchase totals = $812.99       $881.9257   $881.92   $881.90   $882.00