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 $55.34   11.173%   $61.5231   $61.52   $61.50   $61.50  
  Purchase #2 $221.94   13.220%   $251.2805   $251.28   $251.30   $251.30  
  Purchase #3 $107.99   12.763%   $121.7728   $121.77   $121.75   $121.80  
  Purchase #4 $48.75   6.573%   $51.9543   $51.95   $51.95   $52.00  
  Purchase #5 $29.49   8.186%   $31.9041   $31.90   $31.90   $31.90  
  Purchase #6 $240.28   8.683%   $261.1435   $261.14   $261.15   $261.10  
  Purchase #7 $227.77   3.145%   $234.9334   $234.93   $234.95   $234.90  
  7 purchase totals = $931.56       $1,014.5117   $1,014.49   $1,014.50   $1,014.50