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 $61.26   13.805%   $69.7169   $69.72   $69.70   $69.70  
  Purchase #2 $228.98   4.470%   $239.2154   $239.22   $239.20   $239.20  
  Purchase #3 $144.65   9.426%   $158.2847   $158.28   $158.30   $158.30  
  Purchase #4 $32.41   6.672%   $34.5724   $34.57   $34.55   $34.60  
  Purchase #5 $34.74   6.233%   $36.9053   $36.91   $36.90   $36.90  
  Purchase #6 $160.52   10.311%   $177.0712   $177.07   $177.05   $177.10  
  Purchase #7 $50.97   5.428%   $53.7367   $53.74   $53.75   $53.70  
  7 purchase totals = $713.53       $769.5026   $769.51   $769.45   $769.50