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 $58.26   8.233%   $63.0565   $63.06   $63.05   $63.10  
  Purchase #2 $21.37   4.207%   $22.269   $22.27   $22.25   $22.30  
  Purchase #3 $140.81   4.791%   $147.5562   $147.56   $147.55   $147.60  
  Purchase #4 $239.97   7.733%   $258.5269   $258.53   $258.55   $258.50  
  Purchase #5 $120.37   13.857%   $137.0497   $137.05   $137.05   $137.00  
  Purchase #6 $181.84   12.189%   $204.0045   $204.00   $204.00   $204.00  
  Purchase #7 $209.54   4.743%   $219.4785   $219.48   $219.50   $219.50  
  7 purchase totals = $972.16       $1,051.9413   $1,051.95   $1,051.95   $1,052.00