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 $207.89   8.733%   $226.045   $226.05   $226.05   $226.00  
  Purchase #2 $224.58   12.191%   $251.9585   $251.96   $251.95   $252.00  
  Purchase #3 $54.32   4.513%   $56.7715   $56.77   $56.75   $56.80  
  Purchase #4 $119.58   12.375%   $134.378   $134.38   $134.40   $134.40  
  Purchase #5 $113.47   5.713%   $119.9525   $119.95   $119.95   $120.00  
  Purchase #6 $113.46   6.351%   $120.6658   $120.67   $120.65   $120.70  
  Purchase #7 $244.26   13.452%   $277.1179   $277.12   $277.10   $277.10  
  7 purchase totals = $1,077.56       $1,186.8892   $1,186.90   $1,186.85   $1,187.00