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 $71.82   3.557%   $74.3746   $74.37   $74.35   $74.40  
  Purchase #2 $207.57   11.301%   $231.0275   $231.03   $231.05   $231.00  
  Purchase #3 $8.32   11.724%   $9.2954   $9.30   $9.30   $9.30  
  Purchase #4 $196.87   13.326%   $223.1049   $223.10   $223.10   $223.10  
  Purchase #5 $97.28   9.631%   $106.649   $106.65   $106.65   $106.60  
  Purchase #6 $111.91   10.621%   $123.796   $123.80   $123.80   $123.80  
  Purchase #7 $235.67   4.458%   $246.1762   $246.18   $246.20   $246.20  
  7 purchase totals = $929.44       $1,014.4236   $1,014.43   $1,014.45   $1,014.40