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 $72.99   5.458%   $76.9738   $76.97   $76.95   $77.00  
  Purchase #2 $164.48   12.247%   $184.6239   $184.62   $184.60   $184.60  
  Purchase #3 $26.58   6.251%   $28.2415   $28.24   $28.25   $28.20  
  Purchase #4 $192.54   10.573%   $212.8973   $212.90   $212.90   $212.90  
  Purchase #5 $183.38   9.762%   $201.2816   $201.28   $201.30   $201.30  
  Purchase #6 $165.37   8.151%   $178.8493   $178.85   $178.85   $178.80  
  Purchase #7 $225.67   4.180%   $235.103   $235.10   $235.10   $235.10  
  7 purchase totals = $1,031.01       $1,117.9704   $1,117.96   $1,117.95   $1,117.90