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 $181.87   8.621%   $197.549   $197.55   $197.55   $197.50  
  Purchase #2 $98.40   4.253%   $102.585   $102.59   $102.60   $102.60  
  Purchase #3 $132.43   9.259%   $144.6917   $144.69   $144.70   $144.70  
  Purchase #4 $206.47   9.568%   $226.225   $226.23   $226.25   $226.20  
  Purchase #5 $72.90   5.174%   $76.6718   $76.67   $76.65   $76.70  
  Purchase #6 $205.58   7.504%   $221.0067   $221.01   $221.00   $221.00  
  Purchase #7 $117.47   8.430%   $127.3727   $127.37   $127.35   $127.40  
  7 purchase totals = $1,015.12       $1,096.1019   $1,096.11   $1,096.10   $1,096.10