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 $142.79   10.687%   $158.05   $158.05   $158.05   $158.10  
  Purchase #2 $38.45   5.714%   $40.647   $40.65   $40.65   $40.60  
  Purchase #3 $80.70   4.313%   $84.1806   $84.18   $84.20   $84.20  
  Purchase #4 $235.42   12.632%   $265.1583   $265.16   $265.15   $265.20  
  Purchase #5 $114.82   4.580%   $120.0788   $120.08   $120.10   $120.10  
  Purchase #6 $151.45   6.599%   $161.4442   $161.44   $161.45   $161.40  
  Purchase #7 $124.43   6.615%   $132.661   $132.66   $132.65   $132.70  
  7 purchase totals = $888.06       $962.2199   $962.22   $962.25   $962.30