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 $146.36   10.824%   $162.202   $162.20   $162.20   $162.20  
  Purchase #2 $60.71   12.155%   $68.0893   $68.09   $68.10   $68.10  
  Purchase #3 $211.28   3.438%   $218.5438   $218.54   $218.55   $218.50  
  Purchase #4 $229.55   13.421%   $260.3579   $260.36   $260.35   $260.40  
  Purchase #5 $23.92   12.491%   $26.9078   $26.91   $26.90   $26.90  
  Purchase #6 $219.94   4.741%   $230.3674   $230.37   $230.35   $230.40  
  Purchase #7 $221.43   8.166%   $239.512   $239.51   $239.50   $239.50  
  7 purchase totals = $1,113.19       $1,205.9802   $1,205.98   $1,205.95   $1,206.00