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 $57.26   8.312%   $62.0195   $62.02   $62.00   $62.00  
  Purchase #2 $180.47   13.765%   $205.3117   $205.31   $205.30   $205.30  
  Purchase #3 $205.64   12.722%   $231.8015   $231.80   $231.80   $231.80  
  Purchase #4 $171.93   5.676%   $181.6887   $181.69   $181.70   $181.70  
  Purchase #5 $239.91   11.807%   $268.2362   $268.24   $268.25   $268.20  
  Purchase #6 $174.54   12.826%   $196.9265   $196.93   $196.95   $196.90  
  Purchase #7 $133.45   11.635%   $148.9769   $148.98   $149.00   $149.00  
  7 purchase totals = $1,163.20       $1,294.9610   $1,294.97   $1,295.00   $1,294.90