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 $214.68   10.867%   $238.0093   $238.01   $238.00   $238.00  
  Purchase #2 $168.51   5.396%   $177.6028   $177.60   $177.60   $177.60  
  Purchase #3 $116.62   13.125%   $131.9264   $131.93   $131.95   $131.90  
  Purchase #4 $62.87   9.267%   $68.6962   $68.70   $68.70   $68.70  
  Purchase #5 $177.34   13.128%   $200.6212   $200.62   $200.60   $200.60  
  Purchase #6 $163.59   5.847%   $173.1551   $173.16   $173.15   $173.20  
  Purchase #7 $168.65   3.156%   $173.9726   $173.97   $173.95   $174.00  
  7 purchase totals = $1,072.26       $1,163.9836   $1,163.99   $1,163.95   $1,164.00