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 $149.84   11.467%   $167.0222   $167.02   $167.00   $167.00  
  Purchase #2 $204.99   4.688%   $214.5999   $214.60   $214.60   $214.60  
  Purchase #3 $57.76   7.825%   $62.2797   $62.28   $62.30   $62.30  
  Purchase #4 $160.32   3.864%   $166.5148   $166.51   $166.50   $166.50  
  Purchase #5 $222.93   9.494%   $244.095   $244.10   $244.10   $244.10  
  Purchase #6 $179.89   5.773%   $190.275   $190.28   $190.30   $190.30  
  Purchase #7 $207.81   13.642%   $236.1594   $236.16   $236.15   $236.20  
  7 purchase totals = $1,183.54       $1,280.9460   $1,280.95   $1,280.95   $1,281.00