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 $43.59   11.463%   $48.5867   $48.59   $48.60   $48.60  
  Purchase #2 $191.55   9.694%   $210.1189   $210.12   $210.10   $210.10  
  Purchase #3 $67.51   13.551%   $76.6583   $76.66   $76.65   $76.70  
  Purchase #4 $159.51   10.705%   $176.5855   $176.59   $176.60   $176.60  
  Purchase #5 $225.76   7.450%   $242.5791   $242.58   $242.60   $242.60  
  Purchase #6 $161.55   3.866%   $167.7955   $167.80   $167.80   $167.80  
  Purchase #7 $223.75   5.595%   $236.2688   $236.27   $236.25   $236.30  
  7 purchase totals = $1,073.22       $1,158.5928   $1,158.61   $1,158.60   $1,158.70