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 $229.46   10.559%   $253.6887   $253.69   $253.70   $253.70  
  Purchase #2 $39.26   9.417%   $42.9571   $42.96   $42.95   $43.00  
  Purchase #3 $64.29   10.539%   $71.0655   $71.07   $71.05   $71.10  
  Purchase #4 $164.91   7.531%   $177.3294   $177.33   $177.35   $177.30  
  Purchase #5 $70.43   6.299%   $74.8664   $74.87   $74.85   $74.90  
  Purchase #6 $232.91   6.224%   $247.4063   $247.41   $247.40   $247.40  
  Purchase #7 $215.49   6.550%   $229.6046   $229.60   $229.60   $229.60  
  7 purchase totals = $1,016.75       $1,096.9180   $1,096.93   $1,096.90   $1,097.00