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 $65.95   4.632%   $69.0048   $69.00   $69.00   $69.00  
  Purchase #2 $200.29   12.820%   $225.9672   $225.97   $225.95   $226.00  
  Purchase #3 $210.94   6.796%   $225.2755   $225.28   $225.30   $225.30  
  Purchase #4 $241.34   3.321%   $249.3549   $249.35   $249.35   $249.40  
  Purchase #5 $101.97   6.497%   $108.595   $108.60   $108.60   $108.60  
  Purchase #6 $103.53   10.654%   $114.5601   $114.56   $114.55   $114.60  
  Purchase #7 $238.26   13.527%   $270.4894   $270.49   $270.50   $270.50  
  7 purchase totals = $1,162.28       $1,263.2469   $1,263.25   $1,263.25   $1,263.40