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 $219.37   11.544%   $244.6941   $244.69   $244.70   $244.70  
  Purchase #2 $79.83   7.234%   $85.6049   $85.60   $85.60   $85.60  
  Purchase #3 $200.26   6.263%   $212.8023   $212.80   $212.80   $212.80  
  Purchase #4 $35.46   4.683%   $37.1206   $37.12   $37.10   $37.10  
  Purchase #5 $41.84   11.520%   $46.66   $46.66   $46.65   $46.70  
  Purchase #6 $90.26   4.335%   $94.1728   $94.17   $94.15   $94.20  
  Purchase #7 $59.99   11.695%   $67.0058   $67.01   $67.00   $67.00  
  7 purchase totals = $727.01       $788.0605   $788.05   $788.00   $788.10