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 $83.70   13.648%   $95.1234   $95.12   $95.10   $95.10  
  Purchase #2 $228.49   4.512%   $238.7995   $238.80   $238.80   $238.80  
  Purchase #3 $234.63   7.799%   $252.9288   $252.93   $252.95   $252.90  
  Purchase #4 $98.32   4.142%   $102.3924   $102.39   $102.40   $102.40  
  Purchase #5 $119.50   11.627%   $133.3943   $133.39   $133.40   $133.40  
  Purchase #6 $145.95   3.842%   $151.5574   $151.56   $151.55   $151.60  
  Purchase #7 $45.93   8.219%   $49.705   $49.71   $49.70   $49.70  
  7 purchase totals = $956.52       $1,023.9008   $1,023.90   $1,023.90   $1,023.90