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 $177.35   9.741%   $194.6257   $194.63   $194.65   $194.60  
  Purchase #2 $219.82   3.138%   $226.718   $226.72   $226.70   $226.70  
  Purchase #3 $59.62   11.842%   $66.6802   $66.68   $66.70   $66.70  
  Purchase #4 $162.99   13.181%   $184.4737   $184.47   $184.45   $184.50  
  Purchase #5 $234.45   6.145%   $248.857   $248.86   $248.85   $248.90  
  Purchase #6 $149.28   3.443%   $154.4197   $154.42   $154.40   $154.40  
  Purchase #7 $250.32   12.658%   $282.0055   $282.01   $282.00   $282.00  
  7 purchase totals = $1,253.83       $1,357.7798   $1,357.79   $1,357.75   $1,357.80