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 $76.65   11.717%   $85.6311   $85.63   $85.65   $85.60  
  Purchase #2 $192.97   11.757%   $215.6575   $215.66   $215.65   $215.70  
  Purchase #3 $54.57   4.866%   $57.2254   $57.23   $57.25   $57.20  
  Purchase #4 $223.66   3.717%   $231.9734   $231.97   $231.95   $232.00  
  Purchase #5 $158.63   5.822%   $167.8654   $167.87   $167.85   $167.90  
  Purchase #6 $102.81   4.146%   $107.0725   $107.07   $107.05   $107.10  
  Purchase #7 $243.65   11.769%   $272.3252   $272.33   $272.35   $272.30  
  7 purchase totals = $1,052.94       $1,137.7505   $1,137.76   $1,137.75   $1,137.80