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 $214.94   5.609%   $226.996   $227.00   $227.00   $227.00  
  Purchase #2 $76.67   12.317%   $86.1134   $86.11   $86.10   $86.10  
  Purchase #3 $90.87   11.140%   $100.9929   $100.99   $101.00   $101.00  
  Purchase #4 $191.92   7.265%   $205.863   $205.86   $205.85   $205.90  
  Purchase #5 $52.35   7.133%   $56.0841   $56.08   $56.10   $56.10  
  Purchase #6 $153.77   3.867%   $159.7163   $159.72   $159.70   $159.70  
  Purchase #7 $111.87   3.295%   $115.5561   $115.56   $115.55   $115.60  
  7 purchase totals = $892.39       $951.3218   $951.32   $951.30   $951.40