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 $61.92   11.799%   $69.2259   $69.23   $69.25   $69.20  
  Purchase #2 $168.45   3.466%   $174.2885   $174.29   $174.30   $174.30  
  Purchase #3 $227.75   10.539%   $251.7526   $251.75   $251.75   $251.80  
  Purchase #4 $196.54   7.351%   $210.9877   $210.99   $211.00   $211.00  
  Purchase #5 $58.75   12.480%   $66.082   $66.08   $66.10   $66.10  
  Purchase #6 $111.99   10.211%   $123.4253   $123.43   $123.45   $123.40  
  Purchase #7 $144.25   11.695%   $161.12   $161.12   $161.10   $161.10  
  7 purchase totals = $969.65       $1,056.8820   $1,056.89   $1,056.95   $1,056.90