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 $195.34   9.377%   $213.657   $213.66   $213.65   $213.70  
  Purchase #2 $53.64   4.768%   $56.1976   $56.20   $56.20   $56.20  
  Purchase #3 $73.27   6.145%   $77.7724   $77.77   $77.75   $77.80  
  Purchase #4 $155.67   8.218%   $168.463   $168.46   $168.45   $168.50  
  Purchase #5 $51.32   9.814%   $56.3565   $56.36   $56.35   $56.40  
  Purchase #6 $116.98   4.764%   $122.5529   $122.55   $122.55   $122.60  
  Purchase #7 $220.30   13.547%   $250.144   $250.14   $250.15   $250.10  
  7 purchase totals = $866.52       $945.1434   $945.14   $945.10   $945.30