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 $71.50   7.624%   $76.9512   $76.95   $76.95   $77.00  
  Purchase #2 $152.36   12.234%   $170.9997   $171.00   $171.00   $171.00  
  Purchase #3 $8.68   10.151%   $9.5611   $9.56   $9.55   $9.60  
  Purchase #4 $178.97   4.627%   $187.2509   $187.25   $187.25   $187.30  
  Purchase #5 $184.48   12.397%   $207.35   $207.35   $207.35   $207.40  
  Purchase #6 $177.28   4.446%   $185.1619   $185.16   $185.15   $185.20  
  Purchase #7 $222.61   9.602%   $243.985   $243.99   $244.00   $244.00  
  7 purchase totals = $995.88       $1,081.2598   $1,081.26   $1,081.25   $1,081.50