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 $49.98   7.340%   $53.6485   $53.65   $53.65   $53.60  
  Purchase #2 $102.96   4.165%   $107.2483   $107.25   $107.25   $107.20  
  Purchase #3 $165.43   11.230%   $184.0078   $184.01   $184.00   $184.00  
  Purchase #4 $104.83   10.131%   $115.4503   $115.45   $115.45   $115.50  
  Purchase #5 $51.70   3.487%   $53.5028   $53.50   $53.50   $53.50  
  Purchase #6 $219.87   11.423%   $244.9858   $244.99   $245.00   $245.00  
  Purchase #7 $243.27   5.204%   $255.9298   $255.93   $255.95   $255.90  
  7 purchase totals = $938.04       $1,014.7733   $1,014.78   $1,014.80   $1,014.70