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 $114.88   9.616%   $125.9269   $125.93   $125.95   $125.90  
  Purchase #2 $75.42   5.608%   $79.6496   $79.65   $79.65   $79.60  
  Purchase #3 $34.65   9.288%   $37.8683   $37.87   $37.85   $37.90  
  Purchase #4 $95.57   10.733%   $105.8275   $105.83   $105.85   $105.80  
  Purchase #5 $234.46   13.722%   $266.6326   $266.63   $266.65   $266.60  
  Purchase #6 $183.28   4.766%   $192.0151   $192.02   $192.00   $192.00  
  Purchase #7 $223.73   12.550%   $251.8081   $251.81   $251.80   $251.80  
  7 purchase totals = $961.99       $1,059.7281   $1,059.74   $1,059.75   $1,059.60