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 $194.48   4.440%   $203.1149   $203.11   $203.10   $203.10  
  Purchase #2 $176.91   12.286%   $198.6452   $198.65   $198.65   $198.60  
  Purchase #3 $209.94   3.548%   $217.3887   $217.39   $217.40   $217.40  
  Purchase #4 $17.72   8.424%   $19.2127   $19.21   $19.20   $19.20  
  Purchase #5 $231.30   4.488%   $241.6807   $241.68   $241.70   $241.70  
  Purchase #6 $161.55   11.296%   $179.7987   $179.80   $179.80   $179.80  
  Purchase #7 $198.45   8.224%   $214.7705   $214.77   $214.75   $214.80  
  7 purchase totals = $1,190.35       $1,274.6114   $1,274.61   $1,274.60   $1,274.60