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 $68.91   4.486%   $72.0013   $72.00   $72.00   $72.00  
  Purchase #2 $163.66   10.624%   $181.0472   $181.05   $181.05   $181.00  
  Purchase #3 $208.48   6.344%   $221.706   $221.71   $221.70   $221.70  
  Purchase #4 $147.53   5.312%   $155.3668   $155.37   $155.35   $155.40  
  Purchase #5 $134.42   8.178%   $145.4129   $145.41   $145.40   $145.40  
  Purchase #6 $21.98   3.130%   $22.668   $22.67   $22.65   $22.70  
  Purchase #7 $217.29   7.854%   $234.356   $234.36   $234.35   $234.40  
  7 purchase totals = $962.27       $1,032.5582   $1,032.57   $1,032.50   $1,032.60