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 $154.86   12.732%   $174.5768   $174.58   $174.60   $174.60  
  Purchase #2 $166.68   5.473%   $175.8024   $175.80   $175.80   $175.80  
  Purchase #3 $14.70   4.404%   $15.3474   $15.35   $15.35   $15.30  
  Purchase #4 $213.41   9.757%   $234.2324   $234.23   $234.25   $234.20  
  Purchase #5 $155.69   11.147%   $173.0448   $173.04   $173.05   $173.00  
  Purchase #6 $111.82   11.673%   $124.8727   $124.87   $124.85   $124.90  
  Purchase #7 $111.40   4.442%   $116.3484   $116.35   $116.35   $116.30  
  7 purchase totals = $928.56       $1,014.2249   $1,014.22   $1,014.25   $1,014.10