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 $211.96   9.346%   $231.7698   $231.77   $231.75   $231.80  
  Purchase #2 $216.37   10.696%   $239.5129   $239.51   $239.50   $239.50  
  Purchase #3 $169.85   13.658%   $193.0481   $193.05   $193.05   $193.00  
  Purchase #4 $127.87   13.707%   $145.3971   $145.40   $145.40   $145.40  
  Purchase #5 $125.75   9.296%   $137.4397   $137.44   $137.45   $137.40  
  Purchase #6 $127.41   10.696%   $141.0378   $141.04   $141.05   $141.00  
  Purchase #7 $56.35   13.611%   $64.0198   $64.02   $64.00   $64.00  
  7 purchase totals = $1,035.56       $1,152.2252   $1,152.23   $1,152.20   $1,152.10