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 $67.86   8.685%   $73.7536   $73.75   $73.75   $73.80  
  Purchase #2 $86.77   9.463%   $94.981   $94.98   $95.00   $95.00  
  Purchase #3 $31.87   9.330%   $34.8435   $34.84   $34.85   $34.80  
  Purchase #4 $159.61   10.411%   $176.227   $176.23   $176.25   $176.20  
  Purchase #5 $117.92   4.627%   $123.3762   $123.38   $123.40   $123.40  
  Purchase #6 $226.49   5.851%   $239.7419   $239.74   $239.75   $239.70  
  Purchase #7 $186.31   6.628%   $198.6586   $198.66   $198.65   $198.70  
  7 purchase totals = $876.83       $941.5818   $941.58   $941.65   $941.60