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 $233.52   4.357%   $243.6945   $243.69   $243.70   $243.70  
  Purchase #2 $239.27   11.835%   $267.5876   $267.59   $267.60   $267.60  
  Purchase #3 $247.55   12.487%   $278.4616   $278.46   $278.45   $278.50  
  Purchase #4 $203.85   12.714%   $229.7675   $229.77   $229.75   $229.80  
  Purchase #5 $50.55   11.264%   $56.244   $56.24   $56.25   $56.20  
  Purchase #6 $172.26   12.317%   $193.4773   $193.48   $193.50   $193.50  
  Purchase #7 $183.61   7.545%   $197.4634   $197.46   $197.45   $197.50  
  7 purchase totals = $1,330.61       $1,466.6959   $1,466.69   $1,466.70   $1,466.80