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 $23.56   10.237%   $25.9718   $25.97   $25.95   $26.00  
  Purchase #2 $228.32   10.264%   $251.7548   $251.75   $251.75   $251.80  
  Purchase #3 $192.99   6.277%   $205.104   $205.10   $205.10   $205.10  
  Purchase #4 $172.95   7.404%   $185.7552   $185.76   $185.75   $185.80  
  Purchase #5 $239.80   12.247%   $269.1683   $269.17   $269.15   $269.20  
  Purchase #6 $102.86   5.565%   $108.5842   $108.58   $108.60   $108.60  
  Purchase #7 $60.40   8.435%   $65.4947   $65.49   $65.50   $65.50  
  7 purchase totals = $1,020.88       $1,111.8330   $1,111.82   $1,111.80   $1,112.00