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 $60.53   5.257%   $63.7121   $63.71   $63.70   $63.70  
  Purchase #2 $10.81   6.525%   $11.5154   $11.52   $11.50   $11.50  
  Purchase #3 $137.46   11.703%   $153.5469   $153.55   $153.55   $153.50  
  Purchase #4 $172.37   8.495%   $187.0128   $187.01   $187.00   $187.00  
  Purchase #5 $185.70   13.259%   $210.322   $210.32   $210.30   $210.30  
  Purchase #6 $33.95   9.489%   $37.1715   $37.17   $37.15   $37.20  
  Purchase #7 $64.88   6.275%   $68.9512   $68.95   $68.95   $69.00  
  7 purchase totals = $665.70       $732.2319   $732.23   $732.15   $732.20