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 $87.48   8.480%   $94.8983   $94.90   $94.90   $94.90  
  Purchase #2 $130.66   4.317%   $136.3006   $136.30   $136.30   $136.30  
  Purchase #3 $106.25   6.414%   $113.0649   $113.06   $113.05   $113.10  
  Purchase #4 $151.70   8.433%   $164.4929   $164.49   $164.50   $164.50  
  Purchase #5 $43.31   5.474%   $45.6808   $45.68   $45.70   $45.70  
  Purchase #6 $185.62   10.522%   $205.1509   $205.15   $205.15   $205.20  
  Purchase #7 $198.78   3.114%   $204.97   $204.97   $204.95   $205.00  
  7 purchase totals = $903.80       $964.5584   $964.55   $964.55   $964.70