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 $60.27   4.449%   $62.9514   $62.95   $62.95   $63.00  
  Purchase #2 $187.50   6.702%   $200.0663   $200.07   $200.05   $200.10  
  Purchase #3 $56.42   4.108%   $58.7377   $58.74   $58.75   $58.70  
  Purchase #4 $71.74   5.800%   $75.9009   $75.90   $75.90   $75.90  
  Purchase #5 $39.83   10.646%   $44.0703   $44.07   $44.05   $44.10  
  Purchase #6 $212.71   7.318%   $228.2761   $228.28   $228.30   $228.30  
  Purchase #7 $163.74   13.130%   $185.2391   $185.24   $185.25   $185.20  
  7 purchase totals = $792.21       $855.2418   $855.25   $855.25   $855.30