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 $153.96   13.650%   $174.9755   $174.98   $175.00   $175.00  
  Purchase #2 $78.45   10.738%   $86.874   $86.87   $86.85   $86.90  
  Purchase #3 $243.41   9.233%   $265.884   $265.88   $265.90   $265.90  
  Purchase #4 $173.98   7.412%   $186.8754   $186.88   $186.90   $186.90  
  Purchase #5 $236.71   12.133%   $265.43   $265.43   $265.45   $265.40  
  Purchase #6 $226.65   4.651%   $237.1915   $237.19   $237.20   $237.20  
  Purchase #7 $86.75   9.540%   $95.026   $95.03   $95.05   $95.00  
  7 purchase totals = $1,199.91       $1,312.2564   $1,312.26   $1,312.35   $1,312.30