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 $216.67   7.579%   $233.0914   $233.09   $233.10   $233.10  
  Purchase #2 $114.85   10.145%   $126.5015   $126.50   $126.50   $126.50  
  Purchase #3 $160.54   9.640%   $176.0161   $176.02   $176.00   $176.00  
  Purchase #4 $164.72   13.810%   $187.4678   $187.47   $187.45   $187.50  
  Purchase #5 $41.94   3.521%   $43.4167   $43.42   $43.40   $43.40  
  Purchase #6 $114.71   3.467%   $118.687   $118.69   $118.70   $118.70  
  Purchase #7 $174.54   13.740%   $198.5218   $198.52   $198.50   $198.50  
  7 purchase totals = $987.97       $1,083.7023   $1,083.71   $1,083.65   $1,083.70