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 $214.56   10.236%   $236.5224   $236.52   $236.50   $236.50  
  Purchase #2 $50.27   12.548%   $56.5779   $56.58   $56.60   $56.60  
  Purchase #3 $52.86   4.817%   $55.4063   $55.41   $55.40   $55.40  
  Purchase #4 $244.85   7.190%   $262.4547   $262.45   $262.45   $262.50  
  Purchase #5 $181.91   10.704%   $201.3816   $201.38   $201.40   $201.40  
  Purchase #6 $168.72   3.279%   $174.2523   $174.25   $174.25   $174.30  
  Purchase #7 $156.38   9.579%   $171.3596   $171.36   $171.35   $171.40  
  7 purchase totals = $1,069.55       $1,157.9548   $1,157.95   $1,157.95   $1,158.10