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 $124.93   5.680%   $132.026   $132.03   $132.05   $132.00  
  Purchase #2 $126.41   5.111%   $132.8708   $132.87   $132.85   $132.90  
  Purchase #3 $16.92   5.447%   $17.8416   $17.84   $17.85   $17.80  
  Purchase #4 $110.69   11.583%   $123.5112   $123.51   $123.50   $123.50  
  Purchase #5 $211.64   9.457%   $231.6548   $231.65   $231.65   $231.70  
  Purchase #6 $240.53   10.665%   $266.1825   $266.18   $266.20   $266.20  
  Purchase #7 $98.27   3.674%   $101.8804   $101.88   $101.90   $101.90  
  7 purchase totals = $929.39       $1,005.9673   $1,005.96   $1,006.00   $1,006.00