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 $52.62   10.669%   $58.234   $58.23   $58.25   $58.20  
  Purchase #2 $56.39   5.116%   $59.2749   $59.27   $59.25   $59.30  
  Purchase #3 $202.44   3.153%   $208.8229   $208.82   $208.80   $208.80  
  Purchase #4 $226.44   6.286%   $240.674   $240.67   $240.65   $240.70  
  Purchase #5 $226.78   11.704%   $253.3223   $253.32   $253.30   $253.30  
  Purchase #6 $167.63   4.778%   $175.6394   $175.64   $175.65   $175.60  
  Purchase #7 $164.30   10.171%   $181.011   $181.01   $181.00   $181.00  
  7 purchase totals = $1,096.60       $1,176.9785   $1,176.96   $1,176.90   $1,176.90