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 $113.55   11.796%   $126.9444   $126.94   $126.95   $126.90  
  Purchase #2 $125.98   13.212%   $142.6245   $142.62   $142.60   $142.60  
  Purchase #3 $208.43   11.735%   $232.8893   $232.89   $232.90   $232.90  
  Purchase #4 $117.53   9.227%   $128.3745   $128.37   $128.35   $128.40  
  Purchase #5 $106.26   5.214%   $111.8004   $111.80   $111.80   $111.80  
  Purchase #6 $116.47   4.590%   $121.816   $121.82   $121.80   $121.80  
  Purchase #7 $141.25   6.425%   $150.3253   $150.33   $150.35   $150.30  
  7 purchase totals = $929.47       $1,014.7744   $1,014.77   $1,014.75   $1,014.70