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 $56.74   10.457%   $62.6733   $62.67   $62.65   $62.70  
  Purchase #2 $151.59   13.443%   $171.9682   $171.97   $171.95   $172.00  
  Purchase #3 $236.94   6.483%   $252.3008   $252.30   $252.30   $252.30  
  Purchase #4 $61.40   3.869%   $63.7756   $63.78   $63.80   $63.80  
  Purchase #5 $211.99   12.314%   $238.0944   $238.09   $238.10   $238.10  
  Purchase #6 $198.81   13.288%   $225.2279   $225.23   $225.25   $225.20  
  Purchase #7 $56.93   4.518%   $59.5021   $59.50   $59.50   $59.50  
  7 purchase totals = $974.40       $1,073.5423   $1,073.54   $1,073.55   $1,073.60