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 $69.43   10.308%   $76.5868   $76.59   $76.60   $76.60  
  Purchase #2 $221.76   9.580%   $243.0046   $243.00   $243.00   $243.00  
  Purchase #3 $34.45   3.280%   $35.58   $35.58   $35.60   $35.60  
  Purchase #4 $88.96   3.209%   $91.8147   $91.81   $91.80   $91.80  
  Purchase #5 $135.70   11.764%   $151.6637   $151.66   $151.65   $151.70  
  Purchase #6 $233.28   11.370%   $259.8039   $259.80   $259.80   $259.80  
  Purchase #7 $76.51   13.804%   $87.0714   $87.07   $87.05   $87.10  
  7 purchase totals = $860.09       $945.5251   $945.51   $945.50   $945.60