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 $61.42   7.278%   $65.8901   $65.89   $65.90   $65.90  
  Purchase #2 $115.75   3.831%   $120.1844   $120.18   $120.20   $120.20  
  Purchase #3 $241.94   8.578%   $262.6936   $262.69   $262.70   $262.70  
  Purchase #4 $189.97   13.746%   $216.0833   $216.08   $216.10   $216.10  
  Purchase #5 $105.89   8.123%   $114.4914   $114.49   $114.50   $114.50  
  Purchase #6 $244.85   8.205%   $264.9399   $264.94   $264.95   $264.90  
  Purchase #7 $154.92   4.103%   $161.2764   $161.28   $161.30   $161.30  
  7 purchase totals = $1,114.74       $1,205.5591   $1,205.55   $1,205.65   $1,205.60