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 $61.67   10.177%   $67.9462   $67.95   $67.95   $67.90  
  Purchase #2 $223.83   12.788%   $252.4534   $252.45   $252.45   $252.50  
  Purchase #3 $186.26   11.283%   $207.2757   $207.28   $207.30   $207.30  
  Purchase #4 $121.34   3.780%   $125.9267   $125.93   $125.95   $125.90  
  Purchase #5 $199.96   12.670%   $225.2949   $225.29   $225.30   $225.30  
  Purchase #6 $96.83   5.660%   $102.3106   $102.31   $102.30   $102.30  
  Purchase #7 $71.76   9.848%   $78.8269   $78.83   $78.85   $78.80  
  7 purchase totals = $961.65       $1,060.0344   $1,060.04   $1,060.10   $1,060.00