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 $91.26   5.816%   $96.5677   $96.57   $96.55   $96.60  
  Purchase #2 $22.62   9.177%   $24.6958   $24.70   $24.70   $24.70  
  Purchase #3 $214.46   8.798%   $233.3282   $233.33   $233.35   $233.30  
  Purchase #4 $157.85   13.333%   $178.8961   $178.90   $178.90   $178.90  
  Purchase #5 $83.83   9.436%   $91.7402   $91.74   $91.75   $91.70  
  Purchase #6 $113.94   9.424%   $124.6777   $124.68   $124.70   $124.70  
  Purchase #7 $106.90   5.234%   $112.4951   $112.50   $112.50   $112.50  
  7 purchase totals = $790.86       $862.4008   $862.42   $862.45   $862.40