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 $87.90   8.522%   $95.3908   $95.39   $95.40   $95.40  
  Purchase #2 $175.84   9.318%   $192.2248   $192.22   $192.20   $192.20  
  Purchase #3 $146.27   13.283%   $165.699   $165.70   $165.70   $165.70  
  Purchase #4 $153.46   9.583%   $168.1661   $168.17   $168.15   $168.20  
  Purchase #5 $225.71   5.411%   $237.9232   $237.92   $237.90   $237.90  
  Purchase #6 $219.44   8.729%   $238.5949   $238.59   $238.60   $238.60  
  Purchase #7 $65.55   13.388%   $74.3258   $74.33   $74.35   $74.30  
  7 purchase totals = $1,074.17       $1,172.3246   $1,172.32   $1,172.30   $1,172.30