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 $87.69   9.285%   $95.832   $95.83   $95.85   $95.80  
  Purchase #2 $115.74   4.282%   $120.696   $120.70   $120.70   $120.70  
  Purchase #3 $142.87   6.758%   $152.5252   $152.53   $152.55   $152.50  
  Purchase #4 $163.48   6.732%   $174.4855   $174.49   $174.50   $174.50  
  Purchase #5 $25.83   6.525%   $27.5154   $27.52   $27.50   $27.50  
  Purchase #6 $146.43   7.862%   $157.9423   $157.94   $157.95   $157.90  
  Purchase #7 $192.87   8.733%   $209.7133   $209.71   $209.70   $209.70  
  7 purchase totals = $874.91       $938.7097   $938.72   $938.75   $938.60