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 $185.60   8.554%   $201.4762   $201.48   $201.50   $201.50  
  Purchase #2 $115.94   8.162%   $125.403   $125.40   $125.40   $125.40  
  Purchase #3 $5.33   7.489%   $5.7292   $5.73   $5.75   $5.70  
  Purchase #4 $188.77   6.301%   $200.6644   $200.66   $200.65   $200.70  
  Purchase #5 $118.59   7.266%   $127.2067   $127.21   $127.20   $127.20  
  Purchase #6 $182.78   12.647%   $205.8962   $205.90   $205.90   $205.90  
  Purchase #7 $186.51   6.305%   $198.2695   $198.27   $198.25   $198.30  
  7 purchase totals = $983.52       $1,064.6452   $1,064.65   $1,064.65   $1,064.70