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 $52.70   10.273%   $58.1139   $58.11   $58.10   $58.10  
  Purchase #2 $211.26   10.680%   $233.8226   $233.82   $233.80   $233.80  
  Purchase #3 $43.66   13.635%   $49.613   $49.61   $49.60   $49.60  
  Purchase #4 $208.91   4.268%   $217.8263   $217.83   $217.85   $217.80  
  Purchase #5 $163.26   5.471%   $172.192   $172.19   $172.20   $172.20  
  Purchase #6 $61.87   7.158%   $66.2987   $66.30   $66.30   $66.30  
  Purchase #7 $228.45   8.158%   $247.087   $247.09   $247.10   $247.10  
  7 purchase totals = $970.11       $1,044.9535   $1,044.95   $1,044.95   $1,044.90