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 $59.47   4.621%   $62.2181   $62.22   $62.20   $62.20  
  Purchase #2 $240.91   10.694%   $266.6729   $266.67   $266.65   $266.70  
  Purchase #3 $121.66   4.458%   $127.0836   $127.08   $127.10   $127.10  
  Purchase #4 $108.62   10.299%   $119.8068   $119.81   $119.80   $119.80  
  Purchase #5 $183.33   3.818%   $190.3295   $190.33   $190.35   $190.30  
  Purchase #6 $43.96   8.209%   $47.5687   $47.57   $47.55   $47.60  
  Purchase #7 $37.28   10.407%   $41.1597   $41.16   $41.15   $41.20  
  7 purchase totals = $795.23       $854.8393   $854.84   $854.80   $854.90