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 $141.78   13.555%   $160.9983   $161.00   $161.00   $161.00  
  Purchase #2 $98.59   7.712%   $106.1933   $106.19   $106.20   $106.20  
  Purchase #3 $207.95   7.534%   $223.617   $223.62   $223.60   $223.60  
  Purchase #4 $46.58   6.541%   $49.6268   $49.63   $49.65   $49.60  
  Purchase #5 $202.64   4.747%   $212.2593   $212.26   $212.25   $212.30  
  Purchase #6 $207.51   12.233%   $232.8947   $232.89   $232.90   $232.90  
  Purchase #7 $217.48   5.184%   $228.7542   $228.75   $228.75   $228.80  
  7 purchase totals = $1,122.53       $1,214.3436   $1,214.34   $1,214.35   $1,214.40