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 $44.41   7.138%   $47.58   $47.58   $47.60   $47.60  
  Purchase #2 $163.32   11.464%   $182.043   $182.04   $182.05   $182.00  
  Purchase #3 $229.91   5.431%   $242.3964   $242.40   $242.40   $242.40  
  Purchase #4 $179.80   7.499%   $193.2832   $193.28   $193.30   $193.30  
  Purchase #5 $10.65   6.314%   $11.3224   $11.32   $11.30   $11.30  
  Purchase #6 $223.81   5.243%   $235.5444   $235.54   $235.55   $235.50  
  Purchase #7 $220.35   6.239%   $234.0976   $234.10   $234.10   $234.10  
  7 purchase totals = $1,072.25       $1,146.2670   $1,146.26   $1,146.30   $1,146.20