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 $168.41   8.428%   $182.6036   $182.60   $182.60   $182.60  
  Purchase #2 $121.90   4.623%   $127.5354   $127.54   $127.55   $127.50  
  Purchase #3 $61.80   9.697%   $67.7927   $67.79   $67.80   $67.80  
  Purchase #4 $227.90   4.305%   $237.7111   $237.71   $237.70   $237.70  
  Purchase #5 $143.63   5.712%   $151.8341   $151.83   $151.85   $151.80  
  Purchase #6 $163.65   4.597%   $171.173   $171.17   $171.15   $171.20  
  Purchase #7 $44.84   4.790%   $46.9878   $46.99   $47.00   $47.00  
  7 purchase totals = $932.13       $985.6377   $985.63   $985.65   $985.60