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 $62.64   8.639%   $68.0515   $68.05   $68.05   $68.10  
  Purchase #2 $197.77   9.724%   $217.0012   $217.00   $217.00   $217.00  
  Purchase #3 $99.77   6.289%   $106.0445   $106.04   $106.05   $106.00  
  Purchase #4 $104.40   13.602%   $118.6005   $118.60   $118.60   $118.60  
  Purchase #5 $35.51   10.823%   $39.3532   $39.35   $39.35   $39.40  
  Purchase #6 $103.86   3.677%   $107.6789   $107.68   $107.70   $107.70  
  Purchase #7 $74.37   3.804%   $77.199   $77.20   $77.20   $77.20  
  7 purchase totals = $678.32       $733.9288   $733.92   $733.95   $734.00