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 $53.44   13.450%   $60.6277   $60.63   $60.65   $60.60  
  Purchase #2 $62.60   7.581%   $67.3457   $67.35   $67.35   $67.30  
  Purchase #3 $247.51   3.789%   $256.8882   $256.89   $256.90   $256.90  
  Purchase #4 $229.78   11.479%   $256.1564   $256.16   $256.15   $256.20  
  Purchase #5 $228.51   10.588%   $252.7046   $252.70   $252.70   $252.70  
  Purchase #6 $249.28   8.413%   $270.2519   $270.25   $270.25   $270.30  
  Purchase #7 $182.88   13.793%   $208.1046   $208.10   $208.10   $208.10  
  7 purchase totals = $1,254.00       $1,372.0791   $1,372.08   $1,372.10   $1,372.10