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 $44.74   10.193%   $49.3003   $49.30   $49.30   $49.30  
  Purchase #2 $92.43   3.129%   $95.3221   $95.32   $95.30   $95.30  
  Purchase #3 $169.92   13.278%   $192.482   $192.48   $192.50   $192.50  
  Purchase #4 $112.40   13.805%   $127.9168   $127.92   $127.90   $127.90  
  Purchase #5 $228.52   4.759%   $239.3953   $239.40   $239.40   $239.40  
  Purchase #6 $177.37   13.607%   $201.5047   $201.50   $201.50   $201.50  
  Purchase #7 $136.76   13.198%   $154.8096   $154.81   $154.80   $154.80  
  7 purchase totals = $962.14       $1,060.7308   $1,060.73   $1,060.70   $1,060.70