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 $63.50   9.532%   $69.5528   $69.55   $69.55   $69.60  
  Purchase #2 $241.42   5.489%   $254.6715   $254.67   $254.65   $254.70  
  Purchase #3 $74.86   12.549%   $84.2542   $84.25   $84.25   $84.30  
  Purchase #4 $158.66   11.143%   $176.3395   $176.34   $176.35   $176.30  
  Purchase #5 $235.61   5.868%   $249.4356   $249.44   $249.45   $249.40  
  Purchase #6 $216.35   9.214%   $236.2845   $236.28   $236.30   $236.30  
  Purchase #7 $20.57   3.640%   $21.3187   $21.32   $21.30   $21.30  
  7 purchase totals = $1,010.97       $1,091.8568   $1,091.85   $1,091.85   $1,091.90