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 $84.84   12.693%   $95.6087   $95.61   $95.60   $95.60  
  Purchase #2 $160.26   12.750%   $180.6932   $180.69   $180.70   $180.70  
  Purchase #3 $30.51   11.753%   $34.0958   $34.10   $34.10   $34.10  
  Purchase #4 $160.88   10.453%   $177.6968   $177.70   $177.70   $177.70  
  Purchase #5 $154.69   4.156%   $161.1189   $161.12   $161.10   $161.10  
  Purchase #6 $108.63   6.770%   $115.9843   $115.98   $116.00   $116.00  
  Purchase #7 $113.78   12.119%   $127.569   $127.57   $127.55   $127.60  
  7 purchase totals = $813.59       $892.7667   $892.77   $892.75   $892.80