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 $86.84   11.157%   $96.5287   $96.53   $96.55   $96.50  
  Purchase #2 $246.79   7.801%   $266.0421   $266.04   $266.05   $266.00  
  Purchase #3 $162.29   8.365%   $175.8656   $175.87   $175.85   $175.90  
  Purchase #4 $71.31   12.845%   $80.4698   $80.47   $80.45   $80.50  
  Purchase #5 $221.58   9.357%   $242.3132   $242.31   $242.30   $242.30  
  Purchase #6 $176.35   4.637%   $184.5273   $184.53   $184.55   $184.50  
  Purchase #7 $208.48   4.217%   $217.2716   $217.27   $217.25   $217.30  
  7 purchase totals = $1,173.64       $1,263.0183   $1,263.02   $1,263.00   $1,263.00