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 $203.94   10.670%   $225.7004   $225.70   $225.70   $225.70  
  Purchase #2 $98.35   3.405%   $101.6988   $101.70   $101.70   $101.70  
  Purchase #3 $78.83   10.414%   $87.0394   $87.04   $87.05   $87.00  
  Purchase #4 $119.82   4.867%   $125.6516   $125.65   $125.65   $125.70  
  Purchase #5 $229.80   8.161%   $248.554   $248.55   $248.55   $248.60  
  Purchase #6 $115.39   10.205%   $127.1655   $127.17   $127.15   $127.20  
  Purchase #7 $35.92   4.567%   $37.5605   $37.56   $37.55   $37.60  
  7 purchase totals = $882.05       $953.3702   $953.37   $953.35   $953.50