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 $43.59   5.672%   $46.0624   $46.06   $46.05   $46.10  
  Purchase #2 $85.36   9.417%   $93.3984   $93.40   $93.40   $93.40  
  Purchase #3 $53.62   6.649%   $57.1852   $57.19   $57.20   $57.20  
  Purchase #4 $250.68   8.419%   $271.7847   $271.78   $271.80   $271.80  
  Purchase #5 $80.65   6.602%   $85.9745   $85.97   $85.95   $86.00  
  Purchase #6 $182.86   7.489%   $196.5544   $196.55   $196.55   $196.60  
  Purchase #7 $17.85   11.565%   $19.9144   $19.91   $19.90   $19.90  
  7 purchase totals = $714.61       $770.8740   $770.86   $770.85   $771.00