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 $60.61   3.409%   $62.6762   $62.68   $62.70   $62.70  
  Purchase #2 $162.37   11.126%   $180.4353   $180.44   $180.45   $180.40  
  Purchase #3 $169.54   11.668%   $189.3219   $189.32   $189.30   $189.30  
  Purchase #4 $116.45   10.365%   $128.52   $128.52   $128.50   $128.50  
  Purchase #5 $10.43   5.383%   $10.9914   $10.99   $11.00   $11.00  
  Purchase #6 $114.83   9.235%   $125.4346   $125.43   $125.45   $125.40  
  Purchase #7 $228.51   3.341%   $236.1445   $236.14   $236.15   $236.10  
  7 purchase totals = $862.74       $933.5239   $933.52   $933.55   $933.40