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 $43.49   12.676%   $49.0028   $49.00   $49.00   $49.00  
  Purchase #2 $218.48   3.440%   $225.9957   $226.00   $226.00   $226.00  
  Purchase #3 $32.32   12.590%   $36.3891   $36.39   $36.40   $36.40  
  Purchase #4 $143.71   9.627%   $157.545   $157.55   $157.55   $157.50  
  Purchase #5 $192.78   6.398%   $205.1141   $205.11   $205.10   $205.10  
  Purchase #6 $107.92   5.327%   $113.6689   $113.67   $113.65   $113.70  
  Purchase #7 $220.55   6.363%   $234.5836   $234.58   $234.60   $234.60  
  7 purchase totals = $959.25       $1,022.2992   $1,022.30   $1,022.30   $1,022.30