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 $201.80   6.206%   $214.3237   $214.32   $214.30   $214.30  
  Purchase #2 $205.42   3.571%   $212.7555   $212.76   $212.75   $212.80  
  Purchase #3 $35.76   3.755%   $37.1028   $37.10   $37.10   $37.10  
  Purchase #4 $190.50   9.611%   $208.809   $208.81   $208.80   $208.80  
  Purchase #5 $174.96   11.140%   $194.4505   $194.45   $194.45   $194.50  
  Purchase #6 $61.74   10.825%   $68.4234   $68.42   $68.40   $68.40  
  Purchase #7 $5.75   13.530%   $6.528   $6.53   $6.55   $6.50  
  7 purchase totals = $875.93       $942.3929   $942.39   $942.35   $942.40