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 $176.61   10.789%   $195.6645   $195.66   $195.65   $195.70  
  Purchase #2 $62.77   9.823%   $68.9359   $68.94   $68.95   $68.90  
  Purchase #3 $162.90   8.731%   $177.1228   $177.12   $177.10   $177.10  
  Purchase #4 $35.43   9.310%   $38.7285   $38.73   $38.75   $38.70  
  Purchase #5 $115.76   3.308%   $119.5893   $119.59   $119.60   $119.60  
  Purchase #6 $211.27   10.265%   $232.9569   $232.96   $232.95   $233.00  
  Purchase #7 $33.67   4.293%   $35.1155   $35.12   $35.10   $35.10  
  7 purchase totals = $798.41       $868.1134   $868.12   $868.10   $868.10