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 $223.67   8.724%   $243.183   $243.18   $243.20   $243.20  
  Purchase #2 $167.91   8.741%   $182.587   $182.59   $182.60   $182.60  
  Purchase #3 $76.28   11.602%   $85.13   $85.13   $85.15   $85.10  
  Purchase #4 $57.30   10.118%   $63.0976   $63.10   $63.10   $63.10  
  Purchase #5 $143.93   5.405%   $151.7094   $151.71   $151.70   $151.70  
  Purchase #6 $247.74   10.486%   $273.718   $273.72   $273.70   $273.70  
  Purchase #7 $50.84   6.657%   $54.2244   $54.22   $54.20   $54.20  
  7 purchase totals = $967.67       $1,053.6494   $1,053.65   $1,053.65   $1,053.60