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 $52.36   5.717%   $55.3534   $55.35   $55.35   $55.40  
  Purchase #2 $190.99   8.565%   $207.3483   $207.35   $207.35   $207.30  
  Purchase #3 $227.70   6.209%   $241.8379   $241.84   $241.85   $241.80  
  Purchase #4 $21.43   5.670%   $22.6451   $22.65   $22.65   $22.60  
  Purchase #5 $245.70   8.321%   $266.1447   $266.14   $266.15   $266.10  
  Purchase #6 $246.88   6.397%   $262.6729   $262.67   $262.65   $262.70  
  Purchase #7 $40.74   11.216%   $45.3094   $45.31   $45.30   $45.30  
  7 purchase totals = $1,025.80       $1,101.3117   $1,101.31   $1,101.30   $1,101.20