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 $214.54   5.454%   $226.241   $226.24   $226.25   $226.20  
  Purchase #2 $65.25   5.806%   $69.0384   $69.04   $69.05   $69.00  
  Purchase #3 $9.92   9.602%   $10.8725   $10.87   $10.85   $10.90  
  Purchase #4 $194.58   9.649%   $213.355   $213.36   $213.35   $213.40  
  Purchase #5 $207.98   10.857%   $230.5604   $230.56   $230.55   $230.60  
  Purchase #6 $242.55   3.641%   $251.3812   $251.38   $251.40   $251.40  
  Purchase #7 $101.51   9.636%   $111.2915   $111.29   $111.30   $111.30  
  7 purchase totals = $1,036.33       $1,112.7400   $1,112.74   $1,112.75   $1,112.80