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 $196.32   7.253%   $210.5591   $210.56   $210.55   $210.60  
  Purchase #2 $228.93   6.353%   $243.4739   $243.47   $243.45   $243.50  
  Purchase #3 $165.50   7.546%   $177.9886   $177.99   $178.00   $178.00  
  Purchase #4 $118.49   7.187%   $127.0059   $127.01   $127.00   $127.00  
  Purchase #5 $171.73   10.253%   $189.3375   $189.34   $189.35   $189.30  
  Purchase #6 $226.76   8.585%   $246.2273   $246.23   $246.25   $246.20  
  Purchase #7 $227.67   5.252%   $239.6272   $239.63   $239.65   $239.60  
  7 purchase totals = $1,335.40       $1,434.2195   $1,434.23   $1,434.25   $1,434.20