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 $244.26   4.317%   $254.8047   $254.80   $254.80   $254.80  
  Purchase #2 $246.66   12.501%   $277.495   $277.50   $277.50   $277.50  
  Purchase #3 $207.66   13.255%   $235.1853   $235.19   $235.20   $235.20  
  Purchase #4 $238.72   9.558%   $261.5369   $261.54   $261.55   $261.50  
  Purchase #5 $76.80   13.500%   $87.168   $87.17   $87.15   $87.20  
  Purchase #6 $135.92   11.588%   $151.6704   $151.67   $151.65   $151.70  
  Purchase #7 $95.66   3.468%   $98.9775   $98.98   $99.00   $99.00  
  7 purchase totals = $1,245.68       $1,366.8378   $1,366.85   $1,366.85   $1,366.90