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 $237.57   6.751%   $253.6084   $253.61   $253.60   $253.60  
  Purchase #2 $61.41   12.359%   $68.9997   $69.00   $69.00   $69.00  
  Purchase #3 $221.52   13.852%   $252.205   $252.21   $252.20   $252.20  
  Purchase #4 $81.37   5.868%   $86.1448   $86.14   $86.15   $86.10  
  Purchase #5 $247.70   13.340%   $280.7432   $280.74   $280.75   $280.70  
  Purchase #6 $184.39   3.176%   $190.2462   $190.25   $190.25   $190.20  
  Purchase #7 $226.33   7.442%   $243.1735   $243.17   $243.15   $243.20  
  7 purchase totals = $1,260.29       $1,375.1208   $1,375.12   $1,375.10   $1,375.00