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 $94.62   3.175%   $97.6242   $97.62   $97.60   $97.60  
  Purchase #2 $76.89   6.763%   $82.0901   $82.09   $82.10   $82.10  
  Purchase #3 $5.39   4.124%   $5.6123   $5.61   $5.60   $5.60  
  Purchase #4 $199.35   7.225%   $213.753   $213.75   $213.75   $213.80  
  Purchase #5 $160.94   6.280%   $171.047   $171.05   $171.05   $171.00  
  Purchase #6 $5.55   7.333%   $5.957   $5.96   $5.95   $6.00  
  Purchase #7 $139.46   8.247%   $150.9613   $150.96   $150.95   $151.00  
  7 purchase totals = $682.20       $727.0449   $727.04   $727.00   $727.10