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 $58.42   11.770%   $65.296   $65.30   $65.30   $65.30  
  Purchase #2 $41.85   12.287%   $46.9921   $46.99   $47.00   $47.00  
  Purchase #3 $101.46   4.816%   $106.3463   $106.35   $106.35   $106.30  
  Purchase #4 $127.25   4.109%   $132.4787   $132.48   $132.50   $132.50  
  Purchase #5 $249.69   11.467%   $278.322   $278.32   $278.30   $278.30  
  Purchase #6 $151.94   13.329%   $172.1921   $172.19   $172.20   $172.20  
  Purchase #7 $204.91   4.519%   $214.1699   $214.17   $214.15   $214.20  
  7 purchase totals = $935.52       $1,015.7971   $1,015.80   $1,015.80   $1,015.80