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 $72.91   4.609%   $76.2704   $76.27   $76.25   $76.30  
  Purchase #2 $89.70   6.426%   $95.4641   $95.46   $95.45   $95.50  
  Purchase #3 $231.76   5.619%   $244.7826   $244.78   $244.80   $244.80  
  Purchase #4 $152.43   13.276%   $172.6666   $172.67   $172.65   $172.70  
  Purchase #5 $59.78   6.388%   $63.5987   $63.60   $63.60   $63.60  
  Purchase #6 $213.70   5.829%   $226.1566   $226.16   $226.15   $226.20  
  Purchase #7 $156.40   8.350%   $169.4594   $169.46   $169.45   $169.50  
  7 purchase totals = $976.68       $1,048.3984   $1,048.40   $1,048.35   $1,048.60