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 $88.37   7.815%   $95.2761   $95.28   $95.30   $95.30  
  Purchase #2 $216.61   11.170%   $240.8053   $240.81   $240.80   $240.80  
  Purchase #3 $71.59   13.632%   $81.3491   $81.35   $81.35   $81.30  
  Purchase #4 $235.54   5.634%   $248.8103   $248.81   $248.80   $248.80  
  Purchase #5 $163.89   11.267%   $182.3555   $182.36   $182.35   $182.40  
  Purchase #6 $128.81   11.525%   $143.6554   $143.66   $143.65   $143.70  
  Purchase #7 $49.35   4.337%   $51.4903   $51.49   $51.50   $51.50  
  7 purchase totals = $954.16       $1,043.7420   $1,043.76   $1,043.75   $1,043.80