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 $214.67   7.416%   $230.5899   $230.59   $230.60   $230.60  
  Purchase #2 $89.64   5.188%   $94.2905   $94.29   $94.30   $94.30  
  Purchase #3 $211.65   10.522%   $233.9198   $233.92   $233.90   $233.90  
  Purchase #4 $182.49   11.624%   $203.7026   $203.70   $203.70   $203.70  
  Purchase #5 $24.89   7.460%   $26.7468   $26.75   $26.75   $26.70  
  Purchase #6 $94.61   12.211%   $106.1628   $106.16   $106.15   $106.20  
  Purchase #7 $143.92   8.791%   $156.572   $156.57   $156.55   $156.60  
  7 purchase totals = $961.87       $1,051.9844   $1,051.98   $1,051.95   $1,052.00