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 $248.25   5.678%   $262.3456   $262.35   $262.35   $262.30  
  Purchase #2 $247.98   7.568%   $266.7471   $266.75   $266.75   $266.70  
  Purchase #3 $124.43   13.788%   $141.5864   $141.59   $141.60   $141.60  
  Purchase #4 $214.50   9.518%   $234.9161   $234.92   $234.90   $234.90  
  Purchase #5 $41.92   5.164%   $44.0847   $44.08   $44.10   $44.10  
  Purchase #6 $250.40   3.371%   $258.841   $258.84   $258.85   $258.80  
  Purchase #7 $211.85   5.297%   $223.0717   $223.07   $223.05   $223.10  
  7 purchase totals = $1,339.33       $1,431.5926   $1,431.60   $1,431.60   $1,431.50