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 $241.80   11.137%   $268.7293   $268.73   $268.75   $268.70  
  Purchase #2 $53.57   6.489%   $57.0462   $57.05   $57.05   $57.00  
  Purchase #3 $162.70   7.307%   $174.5885   $174.59   $174.60   $174.60  
  Purchase #4 $198.28   10.386%   $218.8734   $218.87   $218.85   $218.90  
  Purchase #5 $97.27   11.252%   $108.2148   $108.21   $108.20   $108.20  
  Purchase #6 $162.54   7.653%   $174.9792   $174.98   $175.00   $175.00  
  Purchase #7 $191.82   11.358%   $213.6069   $213.61   $213.60   $213.60  
  7 purchase totals = $1,107.98       $1,216.0383   $1,216.04   $1,216.05   $1,216.00