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 $94.40   3.763%   $97.9523   $97.95   $97.95   $98.00  
  Purchase #2 $158.36   6.771%   $169.0826   $169.08   $169.10   $169.10  
  Purchase #3 $129.56   5.608%   $136.8257   $136.83   $136.85   $136.80  
  Purchase #4 $210.83   11.116%   $234.2659   $234.27   $234.25   $234.30  
  Purchase #5 $183.26   12.828%   $206.7686   $206.77   $206.75   $206.80  
  Purchase #6 $41.71   7.371%   $44.7844   $44.78   $44.80   $44.80  
  Purchase #7 $242.99   6.231%   $258.1307   $258.13   $258.15   $258.10  
  7 purchase totals = $1,061.11       $1,147.8102   $1,147.81   $1,147.85   $1,147.90