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 $168.27   8.456%   $182.4989   $182.50   $182.50   $182.50  
  Purchase #2 $186.86   10.234%   $205.9833   $205.98   $206.00   $206.00  
  Purchase #3 $201.60   8.156%   $218.0425   $218.04   $218.05   $218.00  
  Purchase #4 $117.79   4.594%   $123.2013   $123.20   $123.20   $123.20  
  Purchase #5 $69.51   8.510%   $75.4253   $75.43   $75.45   $75.40  
  Purchase #6 $243.37   8.604%   $264.3096   $264.31   $264.30   $264.30  
  Purchase #7 $216.84   4.186%   $225.9169   $225.92   $225.90   $225.90  
  7 purchase totals = $1,204.24       $1,295.3778   $1,295.38   $1,295.40   $1,295.30