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 $109.35   4.474%   $114.2423   $114.24   $114.25   $114.20  
  Purchase #2 $201.66   6.433%   $214.6328   $214.63   $214.65   $214.60  
  Purchase #3 $23.56   10.496%   $26.0329   $26.03   $26.05   $26.00  
  Purchase #4 $124.86   9.867%   $137.1799   $137.18   $137.20   $137.20  
  Purchase #5 $139.89   9.574%   $153.2831   $153.28   $153.30   $153.30  
  Purchase #6 $179.52   12.377%   $201.7392   $201.74   $201.75   $201.70  
  Purchase #7 $197.36   3.326%   $203.9242   $203.92   $203.90   $203.90  
  7 purchase totals = $976.20       $1,051.0344   $1,051.02   $1,051.10   $1,050.90