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 $58.45   11.175%   $64.9818   $64.98   $65.00   $65.00  
  Purchase #2 $210.26   12.347%   $236.2208   $236.22   $236.20   $236.20  
  Purchase #3 $106.39   12.661%   $119.86   $119.86   $119.85   $119.90  
  Purchase #4 $232.76   4.420%   $243.048   $243.05   $243.05   $243.00  
  Purchase #5 $31.92   8.320%   $34.5757   $34.58   $34.60   $34.60  
  Purchase #6 $249.28   11.836%   $278.7848   $278.78   $278.80   $278.80  
  Purchase #7 $74.40   9.111%   $81.1786   $81.18   $81.20   $81.20  
  7 purchase totals = $963.46       $1,058.6497   $1,058.65   $1,058.70   $1,058.70