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 $114.53   9.720%   $125.6623   $125.66   $125.65   $125.70  
  Purchase #2 $31.73   7.148%   $33.9981   $34.00   $34.00   $34.00  
  Purchase #3 $120.60   8.138%   $130.4144   $130.41   $130.40   $130.40  
  Purchase #4 $127.55   9.435%   $139.5843   $139.58   $139.60   $139.60  
  Purchase #5 $210.63   7.521%   $226.4715   $226.47   $226.45   $226.50  
  Purchase #6 $175.90   5.258%   $185.1488   $185.15   $185.15   $185.10  
  Purchase #7 $66.92   10.696%   $74.0778   $74.08   $74.10   $74.10  
  7 purchase totals = $847.86       $915.3572   $915.35   $915.35   $915.40