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 $67.97   7.536%   $73.0922   $73.09   $73.10   $73.10  
  Purchase #2 $198.49   4.422%   $207.2672   $207.27   $207.25   $207.30  
  Purchase #3 $124.86   9.335%   $136.5157   $136.52   $136.50   $136.50  
  Purchase #4 $125.84   13.286%   $142.5591   $142.56   $142.55   $142.60  
  Purchase #5 $175.60   11.571%   $195.9187   $195.92   $195.90   $195.90  
  Purchase #6 $241.54   8.534%   $262.153   $262.15   $262.15   $262.20  
  Purchase #7 $11.94   3.637%   $12.3743   $12.37   $12.35   $12.40  
  7 purchase totals = $946.24       $1,029.8802   $1,029.88   $1,029.80   $1,030.00