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 $76.38   13.730%   $86.867   $86.87   $86.85   $86.90  
  Purchase #2 $214.93   3.680%   $222.8394   $222.84   $222.85   $222.80  
  Purchase #3 $11.42   8.870%   $12.433   $12.43   $12.45   $12.40  
  Purchase #4 $224.99   4.182%   $234.3991   $234.40   $234.40   $234.40  
  Purchase #5 $184.89   8.405%   $200.43   $200.43   $200.45   $200.40  
  Purchase #6 $185.99   3.769%   $193   $193.00   $193.00   $193.00  
  Purchase #7 $69.52   8.474%   $75.4111   $75.41   $75.40   $75.40  
  7 purchase totals = $968.12       $1,025.3796   $1,025.38   $1,025.40   $1,025.30