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 $61.95   11.628%   $69.1535   $69.15   $69.15   $69.20  
  Purchase #2 $95.73   7.826%   $103.2218   $103.22   $103.20   $103.20  
  Purchase #3 $192.68   7.572%   $207.2697   $207.27   $207.25   $207.30  
  Purchase #4 $231.58   10.348%   $255.5439   $255.54   $255.55   $255.50  
  Purchase #5 $50.91   13.864%   $57.9682   $57.97   $57.95   $58.00  
  Purchase #6 $163.53   11.505%   $182.3441   $182.34   $182.35   $182.30  
  Purchase #7 $133.90   13.558%   $152.0542   $152.05   $152.05   $152.10  
  7 purchase totals = $930.28       $1,027.5554   $1,027.54   $1,027.50   $1,027.60