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 $23.91   8.572%   $25.9596   $25.96   $25.95   $26.00  
  Purchase #2 $249.84   8.302%   $270.5817   $270.58   $270.60   $270.60  
  Purchase #3 $185.42   11.193%   $206.1741   $206.17   $206.15   $206.20  
  Purchase #4 $128.35   6.504%   $136.6979   $136.70   $136.70   $136.70  
  Purchase #5 $209.77   13.691%   $238.4896   $238.49   $238.50   $238.50  
  Purchase #6 $147.81   8.813%   $160.8365   $160.84   $160.85   $160.80  
  Purchase #7 $160.65   11.352%   $178.887   $178.89   $178.90   $178.90  
  7 purchase totals = $1,105.75       $1,217.6264   $1,217.63   $1,217.65   $1,217.70