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 $87.44   9.182%   $95.4687   $95.47   $95.45   $95.50  
  Purchase #2 $200.54   13.790%   $228.1945   $228.19   $228.20   $228.20  
  Purchase #3 $40.25   3.311%   $41.5827   $41.58   $41.60   $41.60  
  Purchase #4 $106.51   13.817%   $121.2265   $121.23   $121.25   $121.20  
  Purchase #5 $223.74   11.779%   $250.0943   $250.09   $250.10   $250.10  
  Purchase #6 $138.80   12.493%   $156.1403   $156.14   $156.15   $156.10  
  Purchase #7 $198.59   8.442%   $215.355   $215.36   $215.35   $215.40  
  7 purchase totals = $995.87       $1,108.0620   $1,108.06   $1,108.10   $1,108.10