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 $88.39   10.396%   $97.579   $97.58   $97.60   $97.60  
  Purchase #2 $56.99   8.749%   $61.9761   $61.98   $62.00   $62.00  
  Purchase #3 $108.93   5.385%   $114.7959   $114.80   $114.80   $114.80  
  Purchase #4 $213.36   3.300%   $220.4009   $220.40   $220.40   $220.40  
  Purchase #5 $245.55   11.339%   $273.3929   $273.39   $273.40   $273.40  
  Purchase #6 $182.86   10.117%   $201.3599   $201.36   $201.35   $201.40  
  Purchase #7 $97.38   6.599%   $103.8061   $103.81   $103.80   $103.80  
  7 purchase totals = $993.46       $1,073.3108   $1,073.32   $1,073.35   $1,073.40