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 $187.65   9.525%   $205.5237   $205.52   $205.50   $205.50  
  Purchase #2 $193.39   6.515%   $205.9894   $205.99   $206.00   $206.00  
  Purchase #3 $80.66   7.625%   $86.8103   $86.81   $86.80   $86.80  
  Purchase #4 $119.29   10.856%   $132.2401   $132.24   $132.25   $132.20  
  Purchase #5 $15.98   4.436%   $16.6889   $16.69   $16.70   $16.70  
  Purchase #6 $23.64   12.423%   $26.5768   $26.58   $26.60   $26.60  
  Purchase #7 $75.33   3.801%   $78.1933   $78.19   $78.20   $78.20  
  7 purchase totals = $695.94       $752.0225   $752.02   $752.05   $752.00