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 $117.36   7.334%   $125.9672   $125.97   $125.95   $126.00  
  Purchase #2 $117.61   6.147%   $124.8395   $124.84   $124.85   $124.80  
  Purchase #3 $87.27   4.283%   $91.0078   $91.01   $91.00   $91.00  
  Purchase #4 $204.75   13.107%   $231.5866   $231.59   $231.60   $231.60  
  Purchase #5 $29.61   3.605%   $30.6774   $30.68   $30.70   $30.70  
  Purchase #6 $103.83   8.441%   $112.5943   $112.59   $112.60   $112.60  
  Purchase #7 $202.76   11.535%   $226.1484   $226.15   $226.15   $226.10  
  7 purchase totals = $863.19       $942.8212   $942.83   $942.85   $942.80