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 $86.49   10.552%   $95.6164   $95.62   $95.60   $95.60  
  Purchase #2 $239.78   13.771%   $272.8001   $272.80   $272.80   $272.80  
  Purchase #3 $75.55   11.679%   $84.3735   $84.37   $84.35   $84.40  
  Purchase #4 $192.83   8.750%   $209.7026   $209.70   $209.70   $209.70  
  Purchase #5 $146.78   9.522%   $160.7564   $160.76   $160.75   $160.80  
  Purchase #6 $24.58   7.190%   $26.3473   $26.35   $26.35   $26.30  
  Purchase #7 $203.87   9.718%   $223.6821   $223.68   $223.70   $223.70  
  7 purchase totals = $969.88       $1,073.2784   $1,073.28   $1,073.25   $1,073.30