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 $191.91   5.228%   $201.9431   $201.94   $201.95   $201.90  
  Purchase #2 $57.81   10.788%   $64.0465   $64.05   $64.05   $64.00  
  Purchase #3 $175.33   5.647%   $185.2309   $185.23   $185.25   $185.20  
  Purchase #4 $218.76   3.289%   $225.955   $225.96   $225.95   $226.00  
  Purchase #5 $245.84   10.751%   $272.2703   $272.27   $272.25   $272.30  
  Purchase #6 $219.56   9.631%   $240.7058   $240.71   $240.70   $240.70  
  Purchase #7 $222.47   13.541%   $252.5947   $252.59   $252.60   $252.60  
  7 purchase totals = $1,331.68       $1,442.7463   $1,442.75   $1,442.75   $1,442.70