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 $210.41   10.242%   $231.9602   $231.96   $231.95   $232.00  
  Purchase #2 $147.95   8.368%   $160.3305   $160.33   $160.35   $160.30  
  Purchase #3 $217.80   8.373%   $236.0364   $236.04   $236.05   $236.00  
  Purchase #4 $118.96   8.102%   $128.5981   $128.60   $128.60   $128.60  
  Purchase #5 $103.92   3.220%   $107.2662   $107.27   $107.25   $107.30  
  Purchase #6 $150.34   9.469%   $164.5757   $164.58   $164.60   $164.60  
  Purchase #7 $72.81   4.554%   $76.1258   $76.13   $76.15   $76.10  
  7 purchase totals = $1,022.19       $1,104.8929   $1,104.91   $1,104.95   $1,104.90