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 $176.26   11.462%   $196.4629   $196.46   $196.45   $196.50  
  Purchase #2 $152.92   5.357%   $161.1119   $161.11   $161.10   $161.10  
  Purchase #3 $206.59   11.185%   $229.6971   $229.70   $229.70   $229.70  
  Purchase #4 $80.73   7.200%   $86.5426   $86.54   $86.55   $86.50  
  Purchase #5 $100.77   13.749%   $114.6249   $114.62   $114.60   $114.60  
  Purchase #6 $177.30   9.865%   $194.7906   $194.79   $194.80   $194.80  
  Purchase #7 $117.47   4.718%   $123.0122   $123.01   $123.00   $123.00  
  7 purchase totals = $1,012.04       $1,106.2422   $1,106.23   $1,106.20   $1,106.20