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 $193.84   7.115%   $207.6317   $207.63   $207.65   $207.60  
  Purchase #2 $32.33   8.305%   $35.015   $35.02   $35.00   $35.00  
  Purchase #3 $207.89   8.582%   $225.7311   $225.73   $225.75   $225.70  
  Purchase #4 $101.72   6.361%   $108.1904   $108.19   $108.20   $108.20  
  Purchase #5 $208.61   8.775%   $226.9155   $226.92   $226.90   $226.90  
  Purchase #6 $155.78   11.294%   $173.3738   $173.37   $173.35   $173.40  
  Purchase #7 $93.68   6.120%   $99.4132   $99.41   $99.40   $99.40  
  7 purchase totals = $993.85       $1,076.2707   $1,076.27   $1,076.25   $1,076.20