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 $196.76   5.261%   $207.1115   $207.11   $207.10   $207.10  
  Purchase #2 $17.29   7.563%   $18.5976   $18.60   $18.60   $18.60  
  Purchase #3 $20.55   11.250%   $22.8619   $22.86   $22.85   $22.90  
  Purchase #4 $44.27   3.829%   $45.9651   $45.97   $45.95   $46.00  
  Purchase #5 $10.62   9.489%   $11.6277   $11.63   $11.65   $11.60  
  Purchase #6 $196.83   4.303%   $205.2996   $205.30   $205.30   $205.30  
  Purchase #7 $44.81   12.653%   $50.4798   $50.48   $50.50   $50.50  
  7 purchase totals = $531.13       $561.9432   $561.95   $561.95   $562.00