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 $179.92   8.745%   $195.654   $195.65   $195.65   $195.70  
  Purchase #2 $56.47   9.181%   $61.6545   $61.65   $61.65   $61.70  
  Purchase #3 $211.29   13.693%   $240.2219   $240.22   $240.20   $240.20  
  Purchase #4 $94.99   7.847%   $102.4439   $102.44   $102.45   $102.40  
  Purchase #5 $157.86   11.661%   $176.2681   $176.27   $176.25   $176.30  
  Purchase #6 $33.97   10.635%   $37.5827   $37.58   $37.60   $37.60  
  Purchase #7 $223.45   4.719%   $233.9946   $233.99   $234.00   $234.00  
  7 purchase totals = $957.95       $1,047.8197   $1,047.80   $1,047.80   $1,047.90