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 $194.62   3.280%   $201.0035   $201.00   $201.00   $201.00  
  Purchase #2 $217.55   9.323%   $237.8322   $237.83   $237.85   $237.80  
  Purchase #3 $179.87   6.334%   $191.263   $191.26   $191.25   $191.30  
  Purchase #4 $173.30   12.391%   $194.7736   $194.77   $194.75   $194.80  
  Purchase #5 $146.44   12.430%   $164.6425   $164.64   $164.65   $164.60  
  Purchase #6 $153.34   5.194%   $161.3045   $161.30   $161.30   $161.30  
  Purchase #7 $214.50   5.376%   $226.0315   $226.03   $226.05   $226.00  
  7 purchase totals = $1,279.62       $1,376.8508   $1,376.83   $1,376.85   $1,376.80