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 $44.96   4.359%   $46.9198   $46.92   $46.90   $46.90  
  Purchase #2 $161.44   10.208%   $177.9198   $177.92   $177.90   $177.90  
  Purchase #3 $222.66   11.359%   $247.9519   $247.95   $247.95   $248.00  
  Purchase #4 $6.26   9.335%   $6.8444   $6.84   $6.85   $6.80  
  Purchase #5 $240.92   11.296%   $268.1343   $268.13   $268.15   $268.10  
  Purchase #6 $184.94   3.631%   $191.6552   $191.66   $191.65   $191.70  
  Purchase #7 $91.26   7.376%   $97.9913   $97.99   $98.00   $98.00  
  7 purchase totals = $952.44       $1,037.4167   $1,037.41   $1,037.40   $1,037.40