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 $208.80   7.572%   $224.6103   $224.61   $224.60   $224.60  
  Purchase #2 $247.56   8.370%   $268.2808   $268.28   $268.30   $268.30  
  Purchase #3 $154.80   10.803%   $171.523   $171.52   $171.50   $171.50  
  Purchase #4 $187.33   4.126%   $195.0592   $195.06   $195.05   $195.10  
  Purchase #5 $187.59   10.687%   $207.6377   $207.64   $207.65   $207.60  
  Purchase #6 $237.81   10.834%   $263.5743   $263.57   $263.55   $263.60  
  Purchase #7 $121.73   13.247%   $137.8556   $137.86   $137.85   $137.90  
  7 purchase totals = $1,345.62       $1,468.5409   $1,468.54   $1,468.50   $1,468.60