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 $216.94   10.499%   $239.7165   $239.72   $239.70   $239.70  
  Purchase #2 $54.94   10.571%   $60.7477   $60.75   $60.75   $60.70  
  Purchase #3 $203.46   7.342%   $218.398   $218.40   $218.40   $218.40  
  Purchase #4 $120.39   7.451%   $129.3603   $129.36   $129.35   $129.40  
  Purchase #5 $126.99   8.489%   $137.7702   $137.77   $137.75   $137.80  
  Purchase #6 $173.31   13.443%   $196.6081   $196.61   $196.60   $196.60  
  Purchase #7 $65.37   9.705%   $71.7142   $71.71   $71.70   $71.70  
  7 purchase totals = $961.40       $1,054.3150   $1,054.32   $1,054.25   $1,054.30