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 $186.71   13.359%   $211.6526   $211.65   $211.65   $211.70  
  Purchase #2 $22.41   7.152%   $24.0128   $24.01   $24.00   $24.00  
  Purchase #3 $195.63   3.303%   $202.0917   $202.09   $202.10   $202.10  
  Purchase #4 $54.46   10.414%   $60.1315   $60.13   $60.15   $60.10  
  Purchase #5 $23.47   8.308%   $25.4199   $25.42   $25.40   $25.40  
  Purchase #6 $155.75   8.766%   $169.403   $169.40   $169.40   $169.40  
  Purchase #7 $167.47   9.668%   $183.661   $183.66   $183.65   $183.70  
  7 purchase totals = $805.90       $876.3725   $876.36   $876.35   $876.40