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 $72.45   5.675%   $76.5615   $76.56   $76.55   $76.60  
  Purchase #2 $152.93   13.597%   $173.7239   $173.72   $173.70   $173.70  
  Purchase #3 $81.82   7.333%   $87.8199   $87.82   $87.80   $87.80  
  Purchase #4 $213.47   4.261%   $222.566   $222.57   $222.55   $222.60  
  Purchase #5 $238.65   9.830%   $262.1093   $262.11   $262.10   $262.10  
  Purchase #6 $117.34   7.866%   $126.57   $126.57   $126.55   $126.60  
  Purchase #7 $244.92   13.598%   $278.2242   $278.22   $278.20   $278.20  
  7 purchase totals = $1,121.58       $1,227.5748   $1,227.57   $1,227.45   $1,227.60