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 $92.56   4.597%   $96.815   $96.82   $96.80   $96.80  
  Purchase #2 $160.25   6.759%   $171.0813   $171.08   $171.10   $171.10  
  Purchase #3 $179.50   7.176%   $192.3809   $192.38   $192.40   $192.40  
  Purchase #4 $48.42   11.626%   $54.0493   $54.05   $54.05   $54.00  
  Purchase #5 $13.35   9.725%   $14.6483   $14.65   $14.65   $14.60  
  Purchase #6 $168.92   12.718%   $190.4032   $190.40   $190.40   $190.40  
  Purchase #7 $32.30   7.454%   $34.7076   $34.71   $34.70   $34.70  
  7 purchase totals = $695.30       $754.0856   $754.09   $754.10   $754.00