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 $62.59   7.395%   $67.2185   $67.22   $67.20   $67.20  
  Purchase #2 $207.87   13.528%   $235.9907   $235.99   $236.00   $236.00  
  Purchase #3 $10.46   7.673%   $11.2626   $11.26   $11.25   $11.30  
  Purchase #4 $200.91   13.778%   $228.5914   $228.59   $228.60   $228.60  
  Purchase #5 $137.60   7.308%   $147.6558   $147.66   $147.65   $147.70  
  Purchase #6 $110.45   7.125%   $118.3196   $118.32   $118.30   $118.30  
  Purchase #7 $111.45   13.185%   $126.1447   $126.14   $126.15   $126.10  
  7 purchase totals = $841.33       $935.1833   $935.18   $935.15   $935.20