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 $166.66   9.363%   $182.2644   $182.26   $182.25   $182.30  
  Purchase #2 $173.71   5.857%   $183.8842   $183.88   $183.90   $183.90  
  Purchase #3 $220.32   6.334%   $234.2751   $234.28   $234.30   $234.30  
  Purchase #4 $89.42   8.503%   $97.0234   $97.02   $97.00   $97.00  
  Purchase #5 $219.62   6.575%   $234.06   $234.06   $234.05   $234.10  
  Purchase #6 $41.78   6.391%   $44.4502   $44.45   $44.45   $44.50  
  Purchase #7 $116.48   10.394%   $128.5869   $128.59   $128.60   $128.60  
  7 purchase totals = $1,027.99       $1,104.5442   $1,104.54   $1,104.55   $1,104.70