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 $23.89   11.130%   $26.549   $26.55   $26.55   $26.50  
  Purchase #2 $211.73   6.583%   $225.6682   $225.67   $225.65   $225.70  
  Purchase #3 $142.77   5.397%   $150.4753   $150.48   $150.50   $150.50  
  Purchase #4 $218.71   10.438%   $241.5389   $241.54   $241.55   $241.50  
  Purchase #5 $75.75   11.436%   $84.4128   $84.41   $84.40   $84.40  
  Purchase #6 $116.28   8.366%   $126.008   $126.01   $126.00   $126.00  
  Purchase #7 $229.91   4.236%   $239.649   $239.65   $239.65   $239.60  
  7 purchase totals = $1,019.04       $1,094.3012   $1,094.31   $1,094.30   $1,094.20