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 $176.36   3.569%   $182.6543   $182.65   $182.65   $182.70  
  Purchase #2 $178.91   8.254%   $193.6772   $193.68   $193.70   $193.70  
  Purchase #3 $184.70   10.852%   $204.7436   $204.74   $204.75   $204.70  
  Purchase #4 $159.81   6.603%   $170.3623   $170.36   $170.35   $170.40  
  Purchase #5 $224.46   11.771%   $250.8812   $250.88   $250.90   $250.90  
  Purchase #6 $120.77   5.284%   $127.1515   $127.15   $127.15   $127.20  
  Purchase #7 $219.53   8.243%   $237.6259   $237.63   $237.65   $237.60  
  7 purchase totals = $1,264.54       $1,367.0960   $1,367.09   $1,367.15   $1,367.20