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 $105.45   8.802%   $114.7317   $114.73   $114.75   $114.70  
  Purchase #2 $181.75   6.312%   $193.2221   $193.22   $193.20   $193.20  
  Purchase #3 $238.37   12.550%   $268.2854   $268.29   $268.30   $268.30  
  Purchase #4 $226.58   4.452%   $236.6673   $236.67   $236.65   $236.70  
  Purchase #5 $223.83   6.488%   $238.3521   $238.35   $238.35   $238.40  
  Purchase #6 $119.67   10.671%   $132.44   $132.44   $132.45   $132.40  
  Purchase #7 $173.41   6.236%   $184.2238   $184.22   $184.20   $184.20  
  7 purchase totals = $1,269.06       $1,367.9224   $1,367.92   $1,367.90   $1,367.90