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 $162.46   8.289%   $175.9263   $175.93   $175.95   $175.90  
  Purchase #2 $250.62   10.575%   $277.1231   $277.12   $277.10   $277.10  
  Purchase #3 $147.74   9.856%   $162.3013   $162.30   $162.30   $162.30  
  Purchase #4 $132.99   3.568%   $137.7351   $137.74   $137.75   $137.70  
  Purchase #5 $119.39   13.874%   $135.9542   $135.95   $135.95   $136.00  
  Purchase #6 $115.70   7.127%   $123.9459   $123.95   $123.95   $123.90  
  Purchase #7 $41.52   13.190%   $46.9965   $47.00   $47.00   $47.00  
  7 purchase totals = $970.42       $1,059.9824   $1,059.99   $1,060.00   $1,059.90