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 $200.48   5.261%   $211.0273   $211.03   $211.05   $211.00  
  Purchase #2 $93.81   10.812%   $103.9527   $103.95   $103.95   $104.00  
  Purchase #3 $151.93   5.667%   $160.5399   $160.54   $160.55   $160.50  
  Purchase #4 $181.77   11.506%   $202.6845   $202.68   $202.70   $202.70  
  Purchase #5 $38.27   4.247%   $39.8953   $39.90   $39.90   $39.90  
  Purchase #6 $142.47   4.167%   $148.4067   $148.41   $148.40   $148.40  
  Purchase #7 $54.43   9.470%   $59.5845   $59.58   $59.60   $59.60  
  7 purchase totals = $863.16       $926.0909   $926.09   $926.15   $926.10