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 $174.85   10.115%   $192.5361   $192.54   $192.55   $192.50  
  Purchase #2 $54.61   11.776%   $61.0409   $61.04   $61.05   $61.00  
  Purchase #3 $250.40   6.482%   $266.6309   $266.63   $266.65   $266.60  
  Purchase #4 $53.52   7.589%   $57.5816   $57.58   $57.60   $57.60  
  Purchase #5 $132.42   4.576%   $138.4795   $138.48   $138.50   $138.50  
  Purchase #6 $229.86   10.729%   $254.5217   $254.52   $254.50   $254.50  
  Purchase #7 $181.58   13.839%   $206.7089   $206.71   $206.70   $206.70  
  7 purchase totals = $1,077.24       $1,177.4996   $1,177.50   $1,177.55   $1,177.40