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 $116.45   7.841%   $125.5808   $125.58   $125.60   $125.60  
  Purchase #2 $80.46   10.491%   $88.9011   $88.90   $88.90   $88.90  
  Purchase #3 $213.33   6.527%   $227.254   $227.25   $227.25   $227.30  
  Purchase #4 $49.46   9.166%   $53.9935   $53.99   $54.00   $54.00  
  Purchase #5 $212.34   4.862%   $222.664   $222.66   $222.65   $222.70  
  Purchase #6 $167.46   8.306%   $181.3692   $181.37   $181.35   $181.40  
  Purchase #7 $136.80   5.370%   $144.1462   $144.15   $144.15   $144.10  
  7 purchase totals = $976.30       $1,043.9088   $1,043.90   $1,043.90   $1,044.00