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 $169.94   3.569%   $176.0052   $176.01   $176.00   $176.00  
  Purchase #2 $168.65   7.723%   $181.6748   $181.67   $181.65   $181.70  
  Purchase #3 $206.68   9.715%   $226.759   $226.76   $226.75   $226.80  
  Purchase #4 $153.37   5.482%   $161.7777   $161.78   $161.80   $161.80  
  Purchase #5 $101.44   11.813%   $113.4231   $113.42   $113.40   $113.40  
  Purchase #6 $138.63   10.209%   $152.7827   $152.78   $152.80   $152.80  
  Purchase #7 $84.78   10.153%   $93.3877   $93.39   $93.40   $93.40  
  7 purchase totals = $1,023.49       $1,105.8102   $1,105.81   $1,105.80   $1,105.90