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 $163.61   7.678%   $176.172   $176.17   $176.15   $176.20  
  Purchase #2 $63.45   10.565%   $70.1535   $70.15   $70.15   $70.20  
  Purchase #3 $156.65   9.462%   $171.4722   $171.47   $171.45   $171.50  
  Purchase #4 $197.70   3.534%   $204.6867   $204.69   $204.70   $204.70  
  Purchase #5 $184.52   11.134%   $205.0645   $205.06   $205.05   $205.10  
  Purchase #6 $45.97   10.557%   $50.8231   $50.82   $50.80   $50.80  
  Purchase #7 $134.86   8.207%   $145.928   $145.93   $145.95   $145.90  
  7 purchase totals = $946.76       $1,024.3000   $1,024.29   $1,024.25   $1,024.40