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 $195.54   3.358%   $202.1062   $202.11   $202.10   $202.10  
  Purchase #2 $220.70   10.449%   $243.7609   $243.76   $243.75   $243.80  
  Purchase #3 $33.28   5.169%   $35.0002   $35.00   $35.00   $35.00  
  Purchase #4 $180.66   7.185%   $193.6404   $193.64   $193.65   $193.60  
  Purchase #5 $182.74   9.165%   $199.4881   $199.49   $199.50   $199.50  
  Purchase #6 $98.41   8.872%   $107.1409   $107.14   $107.15   $107.10  
  Purchase #7 $241.44   11.193%   $268.4644   $268.46   $268.45   $268.50  
  7 purchase totals = $1,152.77       $1,249.6011   $1,249.60   $1,249.60   $1,249.60