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 $244.93   7.698%   $263.7847   $263.78   $263.80   $263.80  
  Purchase #2 $157.65   5.497%   $166.316   $166.32   $166.30   $166.30  
  Purchase #3 $208.27   7.586%   $224.0694   $224.07   $224.05   $224.10  
  Purchase #4 $113.51   10.332%   $125.2379   $125.24   $125.25   $125.20  
  Purchase #5 $18.55   5.520%   $19.574   $19.57   $19.55   $19.60  
  Purchase #6 $206.85   11.423%   $230.4785   $230.48   $230.50   $230.50  
  Purchase #7 $158.72   11.679%   $177.2569   $177.26   $177.25   $177.30  
  7 purchase totals = $1,108.48       $1,206.7174   $1,206.72   $1,206.70   $1,206.80