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 $75.53   13.838%   $85.9818   $85.98   $86.00   $86.00  
  Purchase #2 $124.91   12.258%   $140.2215   $140.22   $140.20   $140.20  
  Purchase #3 $147.48   3.543%   $152.7052   $152.71   $152.70   $152.70  
  Purchase #4 $228.40   5.588%   $241.163   $241.16   $241.15   $241.20  
  Purchase #5 $203.53   12.247%   $228.4563   $228.46   $228.45   $228.50  
  Purchase #6 $10.38   10.459%   $11.4656   $11.47   $11.45   $11.50  
  Purchase #7 $203.35   6.728%   $217.0314   $217.03   $217.05   $217.00  
  7 purchase totals = $993.58       $1,077.0248   $1,077.03   $1,077.00   $1,077.10