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 $243.72   10.708%   $269.8175   $269.82   $269.80   $269.80  
  Purchase #2 $34.31   6.547%   $36.5563   $36.56   $36.55   $36.60  
  Purchase #3 $122.36   10.628%   $135.3644   $135.36   $135.35   $135.40  
  Purchase #4 $199.83   4.177%   $208.1769   $208.18   $208.20   $208.20  
  Purchase #5 $202.90   11.174%   $225.572   $225.57   $225.55   $225.60  
  Purchase #6 $167.27   9.650%   $183.4116   $183.41   $183.40   $183.40  
  Purchase #7 $54.42   10.114%   $59.924   $59.92   $59.90   $59.90  
  7 purchase totals = $1,024.81       $1,118.8227   $1,118.82   $1,118.75   $1,118.90