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 $169.61   3.353%   $175.297   $175.30   $175.30   $175.30  
  Purchase #2 $32.55   10.424%   $35.943   $35.94   $35.95   $35.90  
  Purchase #3 $112.37   8.826%   $122.2878   $122.29   $122.30   $122.30  
  Purchase #4 $73.42   5.829%   $77.6997   $77.70   $77.70   $77.70  
  Purchase #5 $226.96   10.863%   $251.6147   $251.61   $251.60   $251.60  
  Purchase #6 $155.76   4.200%   $162.3019   $162.30   $162.30   $162.30  
  Purchase #7 $132.49   3.728%   $137.4292   $137.43   $137.45   $137.40  
  7 purchase totals = $903.16       $962.5733   $962.57   $962.60   $962.50