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 $68.92   3.520%   $71.346   $71.35   $71.35   $71.30  
  Purchase #2 $240.41   9.213%   $262.559   $262.56   $262.55   $262.60  
  Purchase #3 $55.28   9.524%   $60.5449   $60.54   $60.55   $60.50  
  Purchase #4 $218.54   7.162%   $234.1918   $234.19   $234.20   $234.20  
  Purchase #5 $196.37   5.541%   $207.2509   $207.25   $207.25   $207.30  
  Purchase #6 $29.41   11.489%   $32.7889   $32.79   $32.80   $32.80  
  Purchase #7 $184.51   12.343%   $207.2841   $207.28   $207.30   $207.30  
  7 purchase totals = $993.44       $1,075.9656   $1,075.96   $1,076.00   $1,076.00