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 $24.68   5.438%   $26.0221   $26.02   $26.00   $26.00  
  Purchase #2 $158.30   11.696%   $176.8148   $176.81   $176.80   $176.80  
  Purchase #3 $80.66   9.406%   $88.2469   $88.25   $88.25   $88.20  
  Purchase #4 $210.89   12.198%   $236.6144   $236.61   $236.60   $236.60  
  Purchase #5 $221.59   7.427%   $238.0475   $238.05   $238.05   $238.00  
  Purchase #6 $58.91   11.283%   $65.5568   $65.56   $65.55   $65.60  
  Purchase #7 $193.63   4.636%   $202.6067   $202.61   $202.60   $202.60  
  7 purchase totals = $948.66       $1,033.9092   $1,033.91   $1,033.85   $1,033.80