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 $234.65   7.374%   $251.9531   $251.95   $251.95   $252.00  
  Purchase #2 $86.73   11.481%   $96.6875   $96.69   $96.70   $96.70  
  Purchase #3 $8.29   8.163%   $8.9667   $8.97   $8.95   $9.00  
  Purchase #4 $193.97   5.520%   $204.6771   $204.68   $204.70   $204.70  
  Purchase #5 $240.40   9.249%   $262.6346   $262.63   $262.65   $262.60  
  Purchase #6 $110.90   3.378%   $114.6462   $114.65   $114.65   $114.60  
  Purchase #7 $150.28   3.585%   $155.6675   $155.67   $155.65   $155.70  
  7 purchase totals = $1,025.22       $1,095.2327   $1,095.24   $1,095.25   $1,095.30