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 $60.38   3.277%   $62.3587   $62.36   $62.35   $62.40  
  Purchase #2 $76.96   8.418%   $83.4385   $83.44   $83.45   $83.40  
  Purchase #3 $225.62   11.310%   $251.1376   $251.14   $251.15   $251.10  
  Purchase #4 $240.27   4.745%   $251.6708   $251.67   $251.65   $251.70  
  Purchase #5 $59.68   9.721%   $65.4815   $65.48   $65.50   $65.50  
  Purchase #6 $208.47   3.673%   $216.1271   $216.13   $216.15   $216.10  
  Purchase #7 $151.29   11.555%   $168.7716   $168.77   $168.75   $168.80  
  7 purchase totals = $1,022.67       $1,098.9858   $1,098.99   $1,099.00   $1,099.00