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 $119.36   5.540%   $125.9725   $125.97   $125.95   $126.00  
  Purchase #2 $159.50   11.441%   $177.7484   $177.75   $177.75   $177.70  
  Purchase #3 $138.49   12.211%   $155.401   $155.40   $155.40   $155.40  
  Purchase #4 $149.80   11.473%   $166.9866   $166.99   $167.00   $167.00  
  Purchase #5 $146.47   11.362%   $163.1119   $163.11   $163.10   $163.10  
  Purchase #6 $130.91   13.683%   $148.8224   $148.82   $148.80   $148.80  
  Purchase #7 $141.53   10.503%   $156.3949   $156.39   $156.40   $156.40  
  7 purchase totals = $986.06       $1,094.4377   $1,094.43   $1,094.40   $1,094.40