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 $214.93   5.418%   $226.5749   $226.57   $226.55   $226.60  
  Purchase #2 $246.94   8.209%   $267.2113   $267.21   $267.20   $267.20  
  Purchase #3 $225.96   7.660%   $243.2685   $243.27   $243.25   $243.30  
  Purchase #4 $42.82   7.355%   $45.9694   $45.97   $45.95   $46.00  
  Purchase #5 $80.81   3.660%   $83.7676   $83.77   $83.75   $83.80  
  Purchase #6 $180.93   6.193%   $192.135   $192.14   $192.15   $192.10  
  Purchase #7 $14.74   7.245%   $15.8079   $15.81   $15.80   $15.80  
  7 purchase totals = $1,007.13       $1,074.7346   $1,074.74   $1,074.65   $1,074.80