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 $168.76   4.465%   $176.2951   $176.30   $176.30   $176.30  
  Purchase #2 $125.81   12.599%   $141.6608   $141.66   $141.65   $141.70  
  Purchase #3 $145.33   12.462%   $163.441   $163.44   $163.45   $163.40  
  Purchase #4 $75.61   8.210%   $81.8176   $81.82   $81.80   $81.80  
  Purchase #5 $121.76   10.406%   $134.4303   $134.43   $134.45   $134.40  
  Purchase #6 $238.50   3.185%   $246.0962   $246.10   $246.10   $246.10  
  Purchase #7 $101.39   4.548%   $106.0012   $106.00   $106.00   $106.00  
  7 purchase totals = $977.16       $1,049.7422   $1,049.75   $1,049.75   $1,049.70