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 $161.41   9.247%   $176.3356   $176.34   $176.35   $176.30  
  Purchase #2 $223.94   4.557%   $234.1449   $234.14   $234.15   $234.10  
  Purchase #3 $113.69   10.517%   $125.6468   $125.65   $125.65   $125.60  
  Purchase #4 $76.79   5.283%   $80.8468   $80.85   $80.85   $80.80  
  Purchase #5 $237.52   12.591%   $267.4261   $267.43   $267.45   $267.40  
  Purchase #6 $157.88   11.384%   $175.8531   $175.85   $175.85   $175.90  
  Purchase #7 $34.59   4.513%   $36.151   $36.15   $36.15   $36.20  
  7 purchase totals = $1,005.82       $1,096.4043   $1,096.41   $1,096.45   $1,096.30