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 $65.54   10.235%   $72.248   $72.25   $72.25   $72.20  
  Purchase #2 $158.26   11.264%   $176.0864   $176.09   $176.10   $176.10  
  Purchase #3 $240.60   9.781%   $264.1331   $264.13   $264.15   $264.10  
  Purchase #4 $204.51   5.260%   $215.2672   $215.27   $215.25   $215.30  
  Purchase #5 $169.26   13.575%   $192.237   $192.24   $192.25   $192.20  
  Purchase #6 $122.53   11.687%   $136.8501   $136.85   $136.85   $136.90  
  Purchase #7 $146.93   3.461%   $152.0152   $152.02   $152.00   $152.00  
  7 purchase totals = $1,107.63       $1,208.8370   $1,208.85   $1,208.85   $1,208.80