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 $150.33   7.315%   $161.3266   $161.33   $161.35   $161.30  
  Purchase #2 $44.26   9.162%   $48.3151   $48.32   $48.30   $48.30  
  Purchase #3 $249.53   5.364%   $262.9148   $262.91   $262.90   $262.90  
  Purchase #4 $152.54   6.553%   $162.5359   $162.54   $162.55   $162.50  
  Purchase #5 $211.94   10.706%   $234.6303   $234.63   $234.65   $234.60  
  Purchase #6 $207.99   13.643%   $236.3661   $236.37   $236.35   $236.40  
  Purchase #7 $58.50   4.294%   $61.012   $61.01   $61.00   $61.00  
  7 purchase totals = $1,075.09       $1,167.1008   $1,167.11   $1,167.10   $1,167.00