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 $162.28   9.581%   $177.828   $177.83   $177.85   $177.80  
  Purchase #2 $167.34   5.169%   $175.9898   $175.99   $176.00   $176.00  
  Purchase #3 $68.41   5.239%   $71.994   $71.99   $72.00   $72.00  
  Purchase #4 $133.76   4.689%   $140.032   $140.03   $140.05   $140.00  
  Purchase #5 $49.83   13.457%   $56.5356   $56.54   $56.55   $56.50  
  Purchase #6 $64.75   9.137%   $70.6662   $70.67   $70.65   $70.70  
  Purchase #7 $249.49   4.421%   $260.52   $260.52   $260.50   $260.50  
  7 purchase totals = $895.86       $953.5656   $953.57   $953.60   $953.50