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 $84.98   13.677%   $96.6027   $96.60   $96.60   $96.60  
  Purchase #2 $208.43   6.554%   $222.0905   $222.09   $222.10   $222.10  
  Purchase #3 $191.92   5.428%   $202.3374   $202.34   $202.35   $202.30  
  Purchase #4 $26.58   6.410%   $28.2838   $28.28   $28.30   $28.30  
  Purchase #5 $140.78   10.147%   $155.0649   $155.06   $155.05   $155.10  
  Purchase #6 $115.79   9.762%   $127.0934   $127.09   $127.10   $127.10  
  Purchase #7 $111.61   3.668%   $115.7039   $115.70   $115.70   $115.70  
  7 purchase totals = $880.09       $947.1766   $947.16   $947.20   $947.20