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 $55.83   10.717%   $61.8133   $61.81   $61.80   $61.80  
  Purchase #2 $143.97   8.321%   $155.9497   $155.95   $155.95   $155.90  
  Purchase #3 $206.70   12.146%   $231.8058   $231.81   $231.80   $231.80  
  Purchase #4 $91.83   5.352%   $96.7447   $96.74   $96.75   $96.70  
  Purchase #5 $196.25   5.656%   $207.3499   $207.35   $207.35   $207.30  
  Purchase #6 $187.81   3.742%   $194.8379   $194.84   $194.85   $194.80  
  Purchase #7 $211.56   7.568%   $227.5709   $227.57   $227.55   $227.60  
  7 purchase totals = $1,093.95       $1,176.0722   $1,176.07   $1,176.05   $1,175.90