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 $232.97   13.862%   $265.2643   $265.26   $265.25   $265.30  
  Purchase #2 $239.79   6.154%   $254.5467   $254.55   $254.55   $254.50  
  Purchase #3 $167.53   6.868%   $179.036   $179.04   $179.05   $179.00  
  Purchase #4 $211.28   10.520%   $233.5067   $233.51   $233.50   $233.50  
  Purchase #5 $81.80   4.377%   $85.3804   $85.38   $85.40   $85.40  
  Purchase #6 $159.78   9.173%   $174.4366   $174.44   $174.45   $174.40  
  Purchase #7 $239.70   9.483%   $262.4308   $262.43   $262.45   $262.40  
  7 purchase totals = $1,332.85       $1,454.6015   $1,454.61   $1,454.65   $1,454.50