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 $56.97   9.167%   $62.1924   $62.19   $62.20   $62.20  
  Purchase #2 $86.88   10.775%   $96.2413   $96.24   $96.25   $96.20  
  Purchase #3 $57.35   6.830%   $61.267   $61.27   $61.25   $61.30  
  Purchase #4 $41.79   7.529%   $44.9364   $44.94   $44.95   $44.90  
  Purchase #5 $151.46   3.639%   $156.9716   $156.97   $156.95   $157.00  
  Purchase #6 $96.54   9.818%   $106.0183   $106.02   $106.00   $106.00  
  Purchase #7 $222.56   4.178%   $231.8586   $231.86   $231.85   $231.90  
  7 purchase totals = $713.55       $759.4856   $759.49   $759.45   $759.50