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 $206.50   5.847%   $218.5741   $218.57   $218.55   $218.60  
  Purchase #2 $194.45   5.575%   $205.2906   $205.29   $205.30   $205.30  
  Purchase #3 $112.35   11.255%   $124.995   $125.00   $125.00   $125.00  
  Purchase #4 $75.61   8.371%   $81.9393   $81.94   $81.95   $81.90  
  Purchase #5 $213.34   9.369%   $233.3278   $233.33   $233.35   $233.30  
  Purchase #6 $136.54   7.787%   $147.1724   $147.17   $147.15   $147.20  
  Purchase #7 $190.55   6.506%   $202.9472   $202.95   $202.95   $202.90  
  7 purchase totals = $1,129.34       $1,214.2464   $1,214.25   $1,214.25   $1,214.20