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 $232.74   5.584%   $245.7362   $245.74   $245.75   $245.70  
  Purchase #2 $169.31   9.264%   $184.9949   $184.99   $185.00   $185.00  
  Purchase #3 $71.58   5.598%   $75.587   $75.59   $75.60   $75.60  
  Purchase #4 $139.59   6.206%   $148.253   $148.25   $148.25   $148.30  
  Purchase #5 $60.25   6.308%   $64.0506   $64.05   $64.05   $64.10  
  Purchase #6 $114.36   4.579%   $119.5965   $119.60   $119.60   $119.60  
  Purchase #7 $136.94   7.407%   $147.0831   $147.08   $147.10   $147.10  
  7 purchase totals = $924.77       $985.3013   $985.30   $985.35   $985.40