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 $192.67   4.630%   $201.5906   $201.59   $201.60   $201.60  
  Purchase #2 $37.98   9.630%   $41.6375   $41.64   $41.65   $41.60  
  Purchase #3 $243.27   12.549%   $273.798   $273.80   $273.80   $273.80  
  Purchase #4 $159.80   7.624%   $171.9832   $171.98   $172.00   $172.00  
  Purchase #5 $236.59   6.586%   $252.1718   $252.17   $252.15   $252.20  
  Purchase #6 $181.43   10.134%   $199.8161   $199.82   $199.80   $199.80  
  Purchase #7 $113.81   4.274%   $118.6742   $118.67   $118.65   $118.70  
  7 purchase totals = $1,165.55       $1,259.6714   $1,259.67   $1,259.65   $1,259.70