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 $237.34   12.579%   $267.195   $267.20   $267.20   $267.20  
  Purchase #2 $86.54   12.223%   $97.1178   $97.12   $97.10   $97.10  
  Purchase #3 $54.68   12.307%   $61.4095   $61.41   $61.40   $61.40  
  Purchase #4 $177.85   4.726%   $186.2552   $186.26   $186.25   $186.30  
  Purchase #5 $223.51   6.295%   $237.58   $237.58   $237.60   $237.60  
  Purchase #6 $57.77   3.550%   $59.8208   $59.82   $59.80   $59.80  
  Purchase #7 $163.79   8.160%   $177.1553   $177.16   $177.15   $177.20  
  7 purchase totals = $1,001.48       $1,086.5336   $1,086.55   $1,086.50   $1,086.60