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 $211.86   5.132%   $222.7327   $222.73   $222.75   $222.70  
  Purchase #2 $242.76   8.216%   $262.7052   $262.71   $262.70   $262.70  
  Purchase #3 $61.51   8.848%   $66.9524   $66.95   $66.95   $67.00  
  Purchase #4 $100.58   4.835%   $105.443   $105.44   $105.45   $105.40  
  Purchase #5 $163.29   8.549%   $177.2497   $177.25   $177.25   $177.20  
  Purchase #6 $219.82   10.841%   $243.6507   $243.65   $243.65   $243.70  
  Purchase #7 $119.90   7.821%   $129.2774   $129.28   $129.30   $129.30  
  7 purchase totals = $1,119.72       $1,208.0111   $1,208.01   $1,208.05   $1,208.00