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 $86.84   8.874%   $94.5462   $94.55   $94.55   $94.50  
  Purchase #2 $214.97   8.220%   $232.6405   $232.64   $232.65   $232.60  
  Purchase #3 $114.26   5.683%   $120.7534   $120.75   $120.75   $120.80  
  Purchase #4 $232.86   8.256%   $252.0849   $252.08   $252.10   $252.10  
  Purchase #5 $134.83   5.261%   $141.9234   $141.92   $141.90   $141.90  
  Purchase #6 $240.86   9.352%   $263.3852   $263.39   $263.40   $263.40  
  Purchase #7 $151.32   3.751%   $156.996   $157.00   $157.00   $157.00  
  7 purchase totals = $1,175.94       $1,262.3296   $1,262.33   $1,262.35   $1,262.30