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 $186.52   8.477%   $202.3313   $202.33   $202.35   $202.30  
  Purchase #2 $218.58   7.327%   $234.5954   $234.60   $234.60   $234.60  
  Purchase #3 $205.85   6.279%   $218.7753   $218.78   $218.80   $218.80  
  Purchase #4 $192.46   13.172%   $217.8108   $217.81   $217.80   $217.80  
  Purchase #5 $145.28   5.127%   $152.7285   $152.73   $152.75   $152.70  
  Purchase #6 $107.87   5.856%   $114.1869   $114.19   $114.20   $114.20  
  Purchase #7 $121.67   7.834%   $131.2016   $131.20   $131.20   $131.20  
  7 purchase totals = $1,178.23       $1,271.6298   $1,271.64   $1,271.70   $1,271.60