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 $66.36   8.429%   $71.9535   $71.95   $71.95   $72.00  
  Purchase #2 $212.76   11.137%   $236.4551   $236.46   $236.45   $236.50  
  Purchase #3 $222.95   3.177%   $230.0331   $230.03   $230.05   $230.00  
  Purchase #4 $192.52   8.326%   $208.5492   $208.55   $208.55   $208.50  
  Purchase #5 $110.61   11.683%   $123.5326   $123.53   $123.55   $123.50  
  Purchase #6 $54.30   12.234%   $60.9431   $60.94   $60.95   $60.90  
  Purchase #7 $213.90   13.388%   $242.5369   $242.54   $242.55   $242.50  
  7 purchase totals = $1,073.40       $1,174.0035   $1,174.00   $1,174.05   $1,173.90