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 $176.67   10.437%   $195.109   $195.11   $195.10   $195.10  
  Purchase #2 $95.67   3.849%   $99.3523   $99.35   $99.35   $99.40  
  Purchase #3 $219.76   4.341%   $229.2998   $229.30   $229.30   $229.30  
  Purchase #4 $25.53   11.265%   $28.406   $28.41   $28.40   $28.40  
  Purchase #5 $97.71   12.247%   $109.6765   $109.68   $109.70   $109.70  
  Purchase #6 $42.66   4.793%   $44.7047   $44.70   $44.70   $44.70  
  Purchase #7 $169.71   12.564%   $191.0324   $191.03   $191.05   $191.00  
  7 purchase totals = $827.71       $897.5807   $897.58   $897.60   $897.60