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 $235.84   3.329%   $243.6911   $243.69   $243.70   $243.70  
  Purchase #2 $209.63   11.667%   $234.0875   $234.09   $234.10   $234.10  
  Purchase #3 $96.73   10.684%   $107.0646   $107.06   $107.05   $107.10  
  Purchase #4 $233.34   5.189%   $245.448   $245.45   $245.45   $245.40  
  Purchase #5 $192.50   6.584%   $205.1742   $205.17   $205.15   $205.20  
  Purchase #6 $200.31   5.635%   $211.5975   $211.60   $211.60   $211.60  
  Purchase #7 $225.26   5.319%   $237.2416   $237.24   $237.25   $237.20  
  7 purchase totals = $1,393.61       $1,484.3045   $1,484.30   $1,484.30   $1,484.30