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 $101.61   11.709%   $113.5075   $113.51   $113.50   $113.50  
  Purchase #2 $205.55   3.237%   $212.2037   $212.20   $212.20   $212.20  
  Purchase #3 $45.85   13.608%   $52.0893   $52.09   $52.10   $52.10  
  Purchase #4 $158.39   9.651%   $173.6762   $173.68   $173.70   $173.70  
  Purchase #5 $126.29   9.235%   $137.9529   $137.95   $137.95   $138.00  
  Purchase #6 $150.69   9.295%   $164.6966   $164.70   $164.70   $164.70  
  Purchase #7 $186.98   6.646%   $199.4067   $199.41   $199.40   $199.40  
  7 purchase totals = $975.36       $1,053.5329   $1,053.54   $1,053.55   $1,053.60