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 $147.50   5.532%   $155.6597   $155.66   $155.65   $155.70  
  Purchase #2 $214.55   8.776%   $233.3789   $233.38   $233.40   $233.40  
  Purchase #3 $166.78   8.152%   $180.3759   $180.38   $180.40   $180.40  
  Purchase #4 $150.72   10.785%   $166.9752   $166.98   $167.00   $167.00  
  Purchase #5 $68.87   6.365%   $73.2536   $73.25   $73.25   $73.30  
  Purchase #6 $151.44   6.493%   $161.273   $161.27   $161.25   $161.30  
  Purchase #7 $214.65   9.484%   $235.0074   $235.01   $235.00   $235.00  
  7 purchase totals = $1,114.51       $1,205.9237   $1,205.93   $1,205.95   $1,206.10