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 $85.92   10.606%   $95.0327   $95.03   $95.05   $95.00  
  Purchase #2 $250.70   6.866%   $267.9131   $267.91   $267.90   $267.90  
  Purchase #3 $110.82   7.690%   $119.3421   $119.34   $119.35   $119.30  
  Purchase #4 $190.29   9.113%   $207.6311   $207.63   $207.65   $207.60  
  Purchase #5 $174.94   6.376%   $186.0942   $186.09   $186.10   $186.10  
  Purchase #6 $22.61   8.325%   $24.4923   $24.49   $24.50   $24.50  
  Purchase #7 $243.78   4.766%   $255.3986   $255.40   $255.40   $255.40  
  7 purchase totals = $1,079.06       $1,155.9041   $1,155.89   $1,155.95   $1,155.80