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 $244.47   7.518%   $262.8493   $262.85   $262.85   $262.80  
  Purchase #2 $163.32   13.129%   $184.7623   $184.76   $184.75   $184.80  
  Purchase #3 $102.61   7.647%   $110.4566   $110.46   $110.45   $110.50  
  Purchase #4 $174.65   4.249%   $182.0709   $182.07   $182.05   $182.10  
  Purchase #5 $218.71   3.705%   $226.8132   $226.81   $226.80   $226.80  
  Purchase #6 $202.76   11.829%   $226.7445   $226.74   $226.75   $226.70  
  Purchase #7 $218.55   12.388%   $245.624   $245.62   $245.60   $245.60  
  7 purchase totals = $1,325.07       $1,439.3208   $1,439.31   $1,439.25   $1,439.30