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 $89.51   6.422%   $95.2583   $95.26   $95.25   $95.30  
  Purchase #2 $208.40   9.292%   $227.7645   $227.76   $227.75   $227.80  
  Purchase #3 $200.79   12.132%   $225.1498   $225.15   $225.15   $225.10  
  Purchase #4 $8.86   8.688%   $9.6298   $9.63   $9.65   $9.60  
  Purchase #5 $250.39   9.743%   $274.7855   $274.79   $274.80   $274.80  
  Purchase #6 $207.79   12.362%   $233.477   $233.48   $233.50   $233.50  
  Purchase #7 $186.88   4.396%   $195.0952   $195.10   $195.10   $195.10  
  7 purchase totals = $1,152.62       $1,261.1601   $1,261.17   $1,261.20   $1,261.20