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 $220.92   9.103%   $241.0303   $241.03   $241.05   $241.00  
  Purchase #2 $199.36   6.448%   $212.2147   $212.21   $212.20   $212.20  
  Purchase #3 $43.73   6.741%   $46.6778   $46.68   $46.70   $46.70  
  Purchase #4 $175.92   13.612%   $199.8662   $199.87   $199.85   $199.90  
  Purchase #5 $214.98   9.279%   $234.928   $234.93   $234.95   $234.90  
  Purchase #6 $180.54   9.308%   $197.3447   $197.34   $197.35   $197.30  
  Purchase #7 $33.88   5.543%   $35.758   $35.76   $35.75   $35.80  
  7 purchase totals = $1,069.33       $1,167.8197   $1,167.82   $1,167.85   $1,167.80