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 $161.75   8.659%   $175.7559   $175.76   $175.75   $175.80  
  Purchase #2 $187.25   12.865%   $211.3397   $211.34   $211.35   $211.30  
  Purchase #3 $211.45   13.470%   $239.9323   $239.93   $239.95   $239.90  
  Purchase #4 $236.62   3.444%   $244.7692   $244.77   $244.75   $244.80  
  Purchase #5 $210.54   8.365%   $228.1517   $228.15   $228.15   $228.20  
  Purchase #6 $62.61   5.793%   $66.237   $66.24   $66.25   $66.20  
  Purchase #7 $161.67   10.386%   $178.461   $178.46   $178.45   $178.50  
  7 purchase totals = $1,231.89       $1,344.6468   $1,344.65   $1,344.65   $1,344.70