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 $82.25   5.266%   $86.5813   $86.58   $86.60   $86.60  
  Purchase #2 $66.79   13.469%   $75.7859   $75.79   $75.80   $75.80  
  Purchase #3 $217.88   12.299%   $244.6771   $244.68   $244.70   $244.70  
  Purchase #4 $214.56   3.556%   $222.1898   $222.19   $222.20   $222.20  
  Purchase #5 $203.39   5.366%   $214.3039   $214.30   $214.30   $214.30  
  Purchase #6 $123.84   10.673%   $137.0574   $137.06   $137.05   $137.10  
  Purchase #7 $210.74   5.334%   $221.9809   $221.98   $222.00   $222.00  
  7 purchase totals = $1,119.45       $1,202.5763   $1,202.58   $1,202.65   $1,202.70