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 $173.59   13.818%   $197.5767   $197.58   $197.60   $197.60  
  Purchase #2 $155.93   3.868%   $161.9614   $161.96   $161.95   $162.00  
  Purchase #3 $73.71   10.566%   $81.4982   $81.50   $81.50   $81.50  
  Purchase #4 $247.65   8.663%   $269.1039   $269.10   $269.10   $269.10  
  Purchase #5 $210.85   12.552%   $237.3159   $237.32   $237.30   $237.30  
  Purchase #6 $133.77   13.583%   $151.94   $151.94   $151.95   $151.90  
  Purchase #7 $52.99   12.352%   $59.5353   $59.54   $59.55   $59.50  
  7 purchase totals = $1,048.49       $1,158.9314   $1,158.94   $1,158.95   $1,158.90