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 $90.90   5.612%   $96.0013   $96.00   $96.00   $96.00  
  Purchase #2 $162.93   11.508%   $181.68   $181.68   $181.70   $181.70  
  Purchase #3 $217.59   13.606%   $247.1953   $247.20   $247.20   $247.20  
  Purchase #4 $230.93   7.429%   $248.0858   $248.09   $248.10   $248.10  
  Purchase #5 $70.96   3.772%   $73.6366   $73.64   $73.65   $73.60  
  Purchase #6 $162.81   10.113%   $179.275   $179.28   $179.30   $179.30  
  Purchase #7 $117.25   7.741%   $126.3263   $126.33   $126.35   $126.30  
  7 purchase totals = $1,053.37       $1,152.2003   $1,152.22   $1,152.30   $1,152.20