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 $64.65   7.497%   $69.4968   $69.50   $69.50   $69.50  
  Purchase #2 $41.86   3.443%   $43.3012   $43.30   $43.30   $43.30  
  Purchase #3 $41.25   6.866%   $44.0822   $44.08   $44.10   $44.10  
  Purchase #4 $19.98   3.121%   $20.6036   $20.60   $20.60   $20.60  
  Purchase #5 $246.99   10.697%   $273.4105   $273.41   $273.40   $273.40  
  Purchase #6 $94.81   3.272%   $97.9122   $97.91   $97.90   $97.90  
  Purchase #7 $145.56   4.732%   $152.4479   $152.45   $152.45   $152.40  
  7 purchase totals = $655.10       $701.2544   $701.25   $701.25   $701.20