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 $152.28   7.204%   $163.2503   $163.25   $163.25   $163.30  
  Purchase #2 $216.89   4.450%   $226.5416   $226.54   $226.55   $226.50  
  Purchase #3 $73.49   12.620%   $82.7644   $82.76   $82.75   $82.80  
  Purchase #4 $137.39   13.246%   $155.5887   $155.59   $155.60   $155.60  
  Purchase #5 $151.94   8.823%   $165.3457   $165.35   $165.35   $165.30  
  Purchase #6 $152.89   5.524%   $161.3356   $161.34   $161.35   $161.30  
  Purchase #7 $200.33   7.432%   $215.2185   $215.22   $215.20   $215.20  
  7 purchase totals = $1,085.21       $1,170.0448   $1,170.05   $1,170.05   $1,170.00