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 $194.62   5.744%   $205.799   $205.80   $205.80   $205.80  
  Purchase #2 $201.91   3.772%   $209.526   $209.53   $209.55   $209.50  
  Purchase #3 $63.98   7.466%   $68.7567   $68.76   $68.75   $68.80  
  Purchase #4 $152.88   7.143%   $163.8002   $163.80   $163.80   $163.80  
  Purchase #5 $24.83   12.661%   $27.9737   $27.97   $27.95   $28.00  
  Purchase #6 $193.58   8.784%   $210.5841   $210.58   $210.60   $210.60  
  Purchase #7 $214.40   7.546%   $230.5786   $230.58   $230.60   $230.60  
  7 purchase totals = $1,046.20       $1,117.0183   $1,117.02   $1,117.05   $1,117.10