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 $146.27   11.259%   $162.7385   $162.74   $162.75   $162.70  
  Purchase #2 $165.51   11.539%   $184.6082   $184.61   $184.60   $184.60  
  Purchase #3 $211.80   7.583%   $227.8608   $227.86   $227.85   $227.90  
  Purchase #4 $174.81   7.745%   $188.349   $188.35   $188.35   $188.30  
  Purchase #5 $134.45   5.452%   $141.7802   $141.78   $141.80   $141.80  
  Purchase #6 $192.79   6.700%   $205.7069   $205.71   $205.70   $205.70  
  Purchase #7 $87.89   8.337%   $95.2174   $95.22   $95.20   $95.20  
  7 purchase totals = $1,113.52       $1,206.2610   $1,206.27   $1,206.25   $1,206.20