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 $41.65   3.505%   $43.1098   $43.11   $43.10   $43.10  
  Purchase #2 $183.81   3.447%   $190.1459   $190.15   $190.15   $190.10  
  Purchase #3 $86.29   7.206%   $92.5081   $92.51   $92.50   $92.50  
  Purchase #4 $108.59   3.466%   $112.3537   $112.35   $112.35   $112.40  
  Purchase #5 $192.65   6.245%   $204.681   $204.68   $204.70   $204.70  
  Purchase #6 $205.63   7.129%   $220.2894   $220.29   $220.30   $220.30  
  Purchase #7 $49.46   3.376%   $51.1298   $51.13   $51.15   $51.10  
  7 purchase totals = $868.08       $914.2177   $914.22   $914.25   $914.20