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 $201.35   11.406%   $224.316   $224.32   $224.30   $224.30  
  Purchase #2 $191.84   8.181%   $207.5344   $207.53   $207.55   $207.50  
  Purchase #3 $36.41   12.325%   $40.8975   $40.90   $40.90   $40.90  
  Purchase #4 $164.35   3.756%   $170.523   $170.52   $170.50   $170.50  
  Purchase #5 $201.29   6.615%   $214.6053   $214.61   $214.60   $214.60  
  Purchase #6 $241.60   11.294%   $268.8863   $268.89   $268.90   $268.90  
  Purchase #7 $61.94   7.200%   $66.3997   $66.40   $66.40   $66.40  
  7 purchase totals = $1,098.78       $1,193.1622   $1,193.17   $1,193.15   $1,193.10