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 $231.36   6.305%   $245.9472   $245.95   $245.95   $245.90  
  Purchase #2 $242.79   7.337%   $260.6035   $260.60   $260.60   $260.60  
  Purchase #3 $62.48   7.356%   $67.076   $67.08   $67.10   $67.10  
  Purchase #4 $188.37   9.168%   $205.6398   $205.64   $205.65   $205.60  
  Purchase #5 $219.68   9.764%   $241.1296   $241.13   $241.15   $241.10  
  Purchase #6 $213.34   8.773%   $232.0563   $232.06   $232.05   $232.10  
  Purchase #7 $127.40   5.368%   $134.2388   $134.24   $134.25   $134.20  
  7 purchase totals = $1,285.42       $1,386.6912   $1,386.70   $1,386.75   $1,386.60