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 $59.75   5.196%   $62.8546   $62.85   $62.85   $62.90  
  Purchase #2 $226.99   9.686%   $248.9763   $248.98   $249.00   $249.00  
  Purchase #3 $121.71   8.545%   $132.1101   $132.11   $132.10   $132.10  
  Purchase #4 $211.66   11.319%   $235.6178   $235.62   $235.60   $235.60  
  Purchase #5 $215.90   3.271%   $222.9621   $222.96   $222.95   $223.00  
  Purchase #6 $210.76   3.648%   $218.4485   $218.45   $218.45   $218.40  
  Purchase #7 $64.93   10.572%   $71.7944   $71.79   $71.80   $71.80  
  7 purchase totals = $1,111.70       $1,192.7638   $1,192.76   $1,192.75   $1,192.80